Add test for fixed declaration emit type parameter leak

[jakebailey]

Closes #44727, which was actually fixed by #57772.

[jakebailey]

That or it's not fixed, if this type were to be inferred somehow?

[weswigham]

That or it's not fixed, if this type were to be inferred somehow?

If you add a , prop = [null as any as BrokenType<any>][0] does it repro? Looks like it does on the playground.

[jakebailey]

Sure does, so, not fixed. Oh well!

[weswigham]

If you want a fix, the first block in the old related PR (replacing Independent type parameters in the emit with unknown) is probably still the way to go; I don't think the emit's changed all that much.