Merge #5518

Merge #5518

5518: Use resolved paths in SSR rules r=matklad a=davidlattimore

The main user-visible changes are:
* SSR now matches paths based on whether they resolve to the same thing instead of whether they're written the same.
  * So `foo()` won't match `foo()` if it's a different function `foo()`, but will match `bar::foo()` if it's the same `foo`.
* Paths in the replacement will now be rendered with appropriate qualification for their context.
  * For example `foo::Bar` will render as just `Bar` inside the module `foo`, but might render as `baz::foo::Bar` from elsewhere.
* This means that all paths in the search pattern and replacement template must be able to be resolved.
* It now also matters where you invoke SSR from, since paths are resolved relative to wherever that is.
* Search now uses find-uses on paths to locate places to try matching. This means that when a path is present in the pattern, search will generally be pretty fast.
* Function calls can now match method calls again, but this time only if they resolve to the same function.

Co-authored-by: David Lattimore <dml@google.com>