feat: deserialize dm/group channels in interactions

[shiftinv]

Summary

Followup to #1012 - interaction.channel and other channel fields (slash params, channel select menus, ...) in interactions are now proper DMChannel/GroupChannel objects in dms/gdms respectively, instead of PartialMessageable. They don't have recipient data, since the API doesn't provide the field in interactions.

The core addition is this, everything else is primarily documentation/typing adjustments:

disnake/disnake/state.py

Lines 2074 to 2079 in dfaadc6

	if ch_type in (ChannelType.group, ChannelType.private):
	return (
	self._get_private_channel(channel_id)
	# the factory will be a DMChannel or GroupChannel here
	or factory(me=self.user, data=data, state=self) # type: ignore
	)

Checklist

• If code changes were made, then they have been tested
  • I have updated the documentation to reflect the changes
  • I have formatted the code properly by running pdm lint
  • I have type-checked the code by running pdm pyright
• This PR fixes an issue
• This PR adds something new (e.g. new method or parameters)
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, ...)