Fix 22871 - Support aliases to __traits(parameters)

[MoonlightSentinel]

The current implementation had two bugs preventing users from using
the tuple returned by __traits(parameters) bound to an alias:

• the parser rejected typeof(__traits(X)), i.e. a traits without
  parameters. Fixed by removing the check for existing arguments.
• type semantic rejected the alias as invalid and eagerly issued an
  error. Fixed by extending the list of viable traits.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	22871	critical	Using an alias to `__traits(parameters)` causes unknown error

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "stable + dmd#13804"

[maxhaton]

@MoonlightSentinel ping me when this is ready for review

[MoonlightSentinel]

@maxhaton the ifx in the second commit is ready for review. Currently marked as a draft because it includes #22868