fix(Message): flags not being parsed on some edits

[monbrey]

One of those rabbit hole bugs that made me change a few things.

To start with, Message#suppressEmbeds was broken. This is because:

1. Internally that method calls Message#edit({ flags: 4 }).
2. That method then calls MessageManager#edit(this.id, options)
3. MessageManager#edit constructs an APIMessage with this as the target.
4. APIMessage#resolveData only resolves flags if the APIMessage#target is a Message or Interaction.
   https://github.com/discordjs/discord.js/blob/master/src/structures/APIMessage.js#L159-L164

So, I decided that:

1. Message#edit should pass this rather than this.id.
2. MessageManager#edit should pass the whole message to APIMessage#target if provided with one.
3. APIMessage should support MessageManager as a target also, for when making cacheless edits by ID.

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
• This PR changes the library's interface (methods or parameters added)

[iCrawl]

No more mutation, hooray 🧹

Stale