Make cross-file go-to-definition work in the syntax-only server

[DanielRosenwasser]

One of the original motivators for the syntax-only server was to make sure that users could navigate around their project, and inter-file go-to-definition is table-stakes. Some of this is already described in #37713, but the idea is:

// @filename: foo.ts
export interface Stuff {
  foo: string;
}

export function foo(x: Stuff) {
}

// @filename: bar.ts
import { foo } from "./foo";
import * as fooModule from "./foo"

/**/foo()

fooModule./**/foo();

Go to definition on either call to foo should just work. Go to definition on the import path should also work. We can do this by performing a super-basic basic resolution of the path.

If there's an export *, we should consider trying to continue the search too.

[sheetalkamat]

Investigated this on how to go about it..
Instead of doing some magic on the fly, whenever someone asks for LS for semantic operations, create a project that either resolves relative imports only in open file (potentially whole tree with only relative import/export resolutions). (and we can do this when someone asks for completion/quick info instead of when opening the file)
I think this might be simplet than cooking up goto def/completions on the fly.

[DanielRosenwasser]

Does that also mean that we'll get slightly more accurate type information?

For example, if checker.ts is a module, and types.ts is a direct dependency, then in that case would every type reference be resolved?

(CC @minestarks since you had thoughts around different scenarios)