refactor: fully integrate /ws into mainlib

[Qjuh]

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

BREAKING CHANGE: This removes the compatibility layer of WebSocketManager to integrate @discordjs/ws fully into mainlib discord.js without wrapping it.

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)

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[didinele]

@Qjuh You should also search for "deprecate" in the codebase and remove what is related to WS. I've been working on removing stuff from other parts of the codebase, but it's probably best if stuff like https://github.com/discordjs/discord.js/blob/5eabec14d45ef7bdd7f610e84234eb63e726eacd/packages/discord.js/src/errors/ErrorCodes.js was addressed by this PR.

[didinele]

For future ref, this should be merged after #10421 - probably cleaner that way.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 35.48%. Comparing base (cda8d88) to head (7ca7247).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #10420   +/-   ##
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  Coverage   35.48%   35.48%           
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  Files         228      228           
  Lines       14308    14308           
  Branches     1254     1254           
=======================================
  Hits         5077     5077           
  Misses       9187     9187           
  Partials       44       44           

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[vladfrangu]

This needs a rebase