feat(Managers): add customizable caching for managers

[1Computer1]

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

• All managers are actually managers now:

  • Hierarchy is BaseManager :> DataManager :> CachedManager.
  • BaseManager has no cache, DataManager has a cache getter and the resolve methods, CachedManager is the whole thing.

• Customizable cache types for CachedManagers:

  • Anything implementing the Collection interface can be used.
  • You can disable caching now, you're welcome.
  • Example:

// Using a helper method that does reasonable stuff.
const client = new Client({
  makeCache: Options.cacheWithLimits({
    MessageManager: 200, // This is default.
    PresenceManager: 0, // Add more class names here.
  }),
});

// Just do whatever.
const client = new Client({
  makeCache: (manager) => {
    if (manager.name === 'MessageManager') return new LimitedCollection(0);
    return new Coolection();
  }
});

• Breaking changes in summary:

  • The new managers' hierarchy and methods and constructors.
  • ReactionUserManager's constructor, cus it was weird.
  • Moved options related stuff out of Constants into Options.
  • Removed messageCacheMaxSize.

• Things I wanna do but too much work/infeasible with current designs:

  • Caches with async methods. Do this in the rewrite.
  • More cache types, e.g. one that sweeps based on a predicate (replacing the message sweeping). Need more design work.
  • Rename the manager add to something better, how about addToCache? Someone do this please.

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)
• This PR includes breaking changes (methods removed or renamed, parameters moved or removed)

[iCrawl]

This needs a rebase.

Stale

[iCrawl]

This needs a rebase.

Stale

[SpaceEEC]

It might be worth a consideration to make LimitedCollection public again, otherwise you'd have to reimplement it yourself if cacheWithLimits doesn't cut it for somereason.