refactor(Channels): fix incorrectly shared properties

[monbrey]

This addresses a number of issues with various channel properties being defined too generically, resulting in them existing on channel subclasses where they aren't supported by the API.

Changes

• New class BaseGuildTextChannel extends GuildChannel, implements TextBasedChannel
• TextChannel and NewsChannel both extend BaseGuildTextChannel
• rateLimitPerUser now only exists on TextChannel
• GuildChannel#setTopic moved to BaseGuildTextChannel and StageChannel
• GuildChannel#createInvite moved to BaseGuildTextChannel, BaseGuildVoiceChannel and StoreChannel
• GuildChannel#fetchInvites moved to BaseGuildTextChannel, BaseGuildVoiceChannel and StoreChannel
• BaseGuildTextChannel#setType now has override types

Status and versioning classification:

• I know how to update typings and have done so, or typings don't need updating
• This PR includes breaking changes (methods removed or renamed, parameters moved or removed)

[ImRodry]

Should probably link #4831

[Jiralite]

GuildChannel#setTopic moved to BaseGuildTextChannel

Stage channels would receive this method from BaseGuildVoiceChannel which extends GuildChannel, which means this would be lost and needs implementing back in somewhere...

Perhaps just stick it in the stage channel itself? That way, we could customise the description of it as it's a unique case for a stage channel?

[ckohen]

Stage channel topics seem to have no purpose at this point. The api accepts and sends topic on stage channels, but it doesn't exist in the UI. I suspect this is a remnant after moving to stage instances. But, it probably should be added back directly.

[Jiralite]

Is it still documented that it can be used in a stage channel? I see only text channels and announcement channels here upon editing a channel, which is how it is currently called!

Despite the API accepting it, if it does nothing and doesn't seem to be documented... probably best to not add it back in, since stage instances are the way to go right now?

[ckohen]

If its undocumented, lets yeet it.

[iCrawl]

This needs a rebase.

Stale