Fix find-all-refs for import("mod").Foo where Foo is a typedef

[ghost]

Fixes #23863

Needed to fix a few bugs:

• Previously the import tracker was just ignoring ImportType nodes -- added a Debug.assertNever to prevent this from happening in the future.
• We need to consider typedef tags as exports in the import tracker after Always export typedefs #23723
• An ImportType should be considered a type reference.

Discovered #23879 while working on this.

[weswigham]

An ImportType should be considered a type reference.

Specifically, an ImportType without typeof is effectively a type reference. One with typeof is effectively a type query.

[weswigham]

This should probably only be true if !(node.parent as ImportTypeNode).isTypeOf, otherwise it acts like a type query instead.

[ghost]

We do normally consider typeof uses to be references though, e.g.:

const [|x|] = 0;
const y: typeof [|x|] = 0;

[weswigham]

Will the results still be classified correctly if that's picked up here and not where type queries are looked at?

[ghost]

There actually isn't a specific place in find-all-references where we look for type queries -- we basically just look for identifiers with the same name and check for a symbol match.

[sheetalkamat]

But this function is called from getMeaningFromLocation so that means we need to handle this irrespectively to avoid any wrong usage being seeping out.

[weswigham]

I'd include a helpful message here as the second parameter to assertNever, just in case (if the types drift out of sync with reality because of an invalid cast, for example).