types: Inference of guild in MessageManager

[Jiralite]

Please describe the changes this PR makes and why it should be merged:
Consider this:

import { Client, Events } from "discord.js";

declare const client: Client;

client.on(Events.MessageCreate, async message => {
  // Ensure we receive messages only from guilds.
  if (!message.inGuild()) return;

  message; // Type is now Message<true> & Message<boolean>.

  const sentMessage = await message.channel.send("why hello there");

  sentMessage; // Type is Message<boolean>.

  if (sentMessage.inGuild()) {
    sentMessage; // Type is now Message<true> & Message<boolean>.
  }
});

There is no way sentMessage could be from a direct message channel. This is a bit of a nuisance, so the typings have been adjusted to ensure MessageManager knows whether it is in a guild or not. With this pull request, sentMessage will be Message<true>.

Status and versioning classification:

• Code changes have been tested against the Discord API, or there are no code changes
• I know how to update typings and have done so, or typings don't need updating

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Name	Status	Preview	Updated
discord-js	✅ Ready (Inspect)	Visit Preview	Aug 22, 2022 at 8:28AM (UTC)

[codecov]

Codecov Report

Merging #8538 (892f48d) into main (27bbc8f) will decrease coverage by 13.54%.
The diff coverage is n/a.

❗ Current head 892f48d differs from pull request most recent head 1ca12d8. Consider uploading reports for the commit 1ca12d8 to get more accurate results

@@             Coverage Diff              @@
##              main    #8538       +/-   ##
============================================
- Coverage   100.00%   86.45%   -13.55%     
============================================
  Files           39       87       +48     
  Lines         3018     8462     +5444     
  Branches       406     1105      +699     
============================================
+ Hits          3018     7316     +4298     
- Misses           0     1103     +1103     
- Partials         0       43       +43     

Flag	Coverage Δ
builders	100.00% <ø> (ø)
collection	100.00% <ø> (?)
proxy	73.28% <ø> (?)
rest	92.53% <ø> (?)
utilities	100.00% <ø> (?)
voice	64.08% <ø> (?)
ws	59.57% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/builders/src/components/Component.ts	100.00% <0.00%> (ø)
packages/builders/src/components/button/Button.ts	100.00% <0.00%> (ø)
packages/builders/src/interactions/modals/Modal.ts	100.00% <0.00%> (ø)
...s/src/interactions/slashCommands/options/number.ts	100.00% <0.00%> (ø)
.../src/interactions/slashCommands/options/integer.ts	100.00% <0.00%> (ø)
...trategies/context/SimpleContextFetchingStrategy.ts	71.42% <0.00%> (ø)
packages/voice/src/networking/Networking.ts	3.18% <0.00%> (ø)
...es/ws/src/strategies/sharding/IShardingStrategy.ts	100.00% <0.00%> (ø)
packages/voice/src/receive/VoiceReceiver.ts	90.56% <0.00%> (ø)
.../src/strategies/sharding/SimpleShardingStrategy.ts	73.43% <0.00%> (ø)
... and 43 more

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