Migration to discord.py 2.0 (#5600)

* Temporarily set d.py to use latest git revision

* Remove `bot` param to Client.start

* Switch to aware datetimes

A lot of this is removing `.replace(...)` which while not technically
needed, simplifies the code base. There's only a few changes that are
actually necessary here.

* Update to work with new Asset design

* [threads] Update core ModLog API to support threads

- Added proper support for passing `Thread` to `channel`
  when creating/editing case
- Added `parent_channel_id` attribute to Modlog API's Case
    - Added `parent_channel` property that tries to get parent channel
- Updated case's content to show both thread and parent information

* [threads] Disallow usage of threads in some of the commands

- announceset channel
- filter channel clear
- filter channel add
- filter channel remove
- GlobalUniqueObjectFinder converter
    - permissions addglobalrule
    - permissions removeglobalrule
    - permissions removeserverrule
    - Permissions cog does not perform any validation for IDs
      when setting through YAML so that has not been touched
- streamalert twitch/youtube/picarto
- embedset channel
- set ownernotifications adddestination

* [threads] Handle threads in Red's permissions system (Requires)

- Made permissions system apply rules of (only) parent in threads

* [threads] Update embed_requested to support threads

- Threads don't have their own embed settings and inherit from parent

* [threads] Update Red.message_eligible_as_command to support threads

* [threads] Properly handle invocation of [p](un)mutechannel in threads

Usage of a (un)mutechannel will mute/unmute user in the parent channel
if it's invoked in a thread.

* [threads] Update Filter cog to properly handle threads

- `[p]filter channel list` in a threads sends list for parent channel
- Checking for filter hits for a message in a thread checks its parent
  channel's word list. There's no separate word list for threads.

* [threads] Support threads in Audio cog

- Handle threads being notify channels
- Update type hint for `is_query_allowed()`

* [threads] Update type hints and documentation to reflect thread support

- Documented that `{channel}` in CCs might be a thread
- Allowed (documented) usage of threads with `Config.channel()`
    - Separate thread scope is still in the picture though
      if it were to be done, it's going to be in separate in PR
- GuildContext.channel might be Thread

* Use less costy channel check in customcom's on_message_without_command

This isn't needed for d.py 2.0 but whatever...

* Update for in-place edits

* Embed's bool changed behavior, I'm hoping it doesn't affect us

* Address User.permissions_in() removal

* Swap VerificationLevel.extreme with VerificationLevel.highest

* Change to keyword-only parameters

* Change of `Guild.vanity_invite()` return type

* avatar -> display_avatar

* Fix metaclass shenanigans with Converter

* Update Red.add_cog() to be inline with `dpy_commands.Bot.add_cog()`

This means adding `override` keyword-only parameter and causing
small breakage by swapping RuntimeError with discord.ClientException.

* Address all DEP-WARNs

* Remove Context.clean_prefix and use upstream implementation instead

* Remove commands.Literal and use upstream implementation instead

Honestly, this was a rather bad implementation anyway...

Breaking but actually not really - it was provisional.

* Update Command.callback's setter

Support for functools.partial is now built into d.py

* Add new perms in HUMANIZED_PERM mapping (some from d.py 1.7 it seems)

BTW, that should really be in core instead of what we have now...

* Remove the part of do_conversion that has not worked for a long while

* Stop wrapping BadArgument in ConversionFailure

This is breaking but it's best to resolve it like this.

The functionality of ConversionFailure can be replicated with
Context.current_parameter and Context.current_argument.

* Add custom errors for int and float converters

* Remove Command.__call__ as it's now implemented in d.py

* Get rid of _dpy_reimplements

These were reimplemented for the purpose of typing
so it is no longer needed now that d.py is type hinted.

* Add return to Red.remove_cog

* Ensure we don't delete messages that differ only by used sticker

* discord.InvalidArgument->ValueError

* Move from raw <t:...> syntax to discord.utils.format_dt()

* Address AsyncIter removal

* Swap to pos-only for params that are pos-only in upstream

* Update for changes to Command.params

* [threads] Support threads in ignore checks and allow ignoring them

- Updated `[p](un)ignore channel` to accept threads
- Updated `[p]ignore list` to list ignored threads
- Updated logic in `Red.ignored_channel_or_guild()`

Ignores for guild channels now work as follows (only changes for threads):
- if channel is not a thread:
    - check if user has manage channels perm in channel
      and allow command usage if so
    - check if channel is ignored and disallow command usage if so
    - allow command usage if none of the conditions above happened
- if channel is a thread:
    - check if user has manage channels perm in parent channel
      and allow command usage if so
    - check if parent channel is ignored and disallow command usage
      if so
    - check if user has manage thread perm in parent channel
      and allow command usage if so
    - check if thread is ignored and disallow command usage if so
    - allow command usage if none of the conditions above happened

* [partial] Raise TypeError when channel is of PartialMessageable type

- Red.embed_requested
- Red.ignored_channel_or_guild

* [partial] Discard command messages when channel is PartialMessageable

* [threads] Add utilities for checking appropriate perms in both channels & threads

* [threads] Update code to use can_react_in() and @bot_can_react()

* [threads] Update code to use can_send_messages_in

* [threads] Add send_messages_in_threads perm to mute role and overrides

* [threads] Update code to use (bot/user)_can_manage_channel

* [threads] Update [p]diagnoseissues to work with threads

* Type hint fix

* [threads] Patch vendored discord.ext.menus to check proper perms in threads

I guess we've reached time when we have to patch the lib we vendor...

* Make docs generation work with non-final d.py releases

* Update discord.utils.oauth_url() usage

* Swap usage of discord.Embed.Empty/discord.embeds.EmptyEmbed to None

* Update usage of Guild.member_count to work with `None`

* Switch from Guild.vanity_invite() to Guild.vanity_url

* Update startup process to work with d.py's new asynchronous startup

* Use setup_hook() for pre-connect actions

* Update core's add_cog, remove_cog, and load_extension methods

* Update all setup functions to async and add awaits to bot.add_cog calls

* Modernize cogs by using async cog_load and cog_unload

* Address StoreChannel removal

* [partial] Disallow passing PartialMessageable to Case.channel

* [partial] Update cogs and utils to work better with PartialMessageable

- Ignore messages with PartialMessageable channel in CustomCommands cog
- In Filter cog, don't pass channel to modlog.create_case()
  if it's PartialMessageable
- In Trivia cog, only compare channel IDs
- Make `.utils.menus.menu()` work for messages
  with PartialMessageable channel
- Make checks in `.utils.tunnel.Tunnel.communicate()` more rigid

* Add few missing DEP-WARNs

redbot/core/commands/context.py

@@ -11,7 +11,7 @@ from discord.ext.commands import Context as DPYContext
 from .requires import PermState
 from ..utils.chat_formatting import box
 from ..utils.predicates import MessagePredicate
-from ..utils import common_filters
+from ..utils import can_user_react_in, common_filters
 
 if TYPE_CHECKING:
     from .commands import Command
@@ -139,7 +139,7 @@ class Context(DPYContext):
             :code:`True` if adding the reaction succeeded.
         """
         try:
-            if not self.channel.permissions_for(self.me).add_reactions:
+            if not can_user_react_in(self.me, self.channel):
                 raise RuntimeError
             await self.message.add_reaction(reaction)
         except (RuntimeError, discord.HTTPException):
@@ -283,16 +283,6 @@ class Context(DPYContext):
                 allowed_mentions=discord.AllowedMentions(everyone=False, roles=False, users=False),
             )
 
-    @property
-    def clean_prefix(self) -> str:
-        """
-        str: The command prefix, but with a sanitized version of the bot's mention if it was used as prefix.
-        This can be used in a context where discord user mentions might not render properly.
-        """
-        me = self.me
-        pattern = re.compile(rf"<@!?{me.id}>")
-        return pattern.sub(f"@{me.display_name}".replace("\\", r"\\"), self.prefix)
-
     @property
     def me(self) -> Union[discord.ClientUser, discord.Member]:
         """
@@ -349,7 +339,7 @@ if TYPE_CHECKING or os.getenv("BUILDING_DOCS", False):
             ...
 
         @property
-        def channel(self) -> discord.TextChannel:
+        def channel(self) -> Union[discord.TextChannel, discord.Thread]:
             ...
 
         @property