Quick Open is slow to open an exact relative path in large workspaces

Does this issue occur when all extensions are disabled?: Yes

- VS Code Version: 1.129.0
- OS Version: OS-independent

Steps to Reproduce:

1. Open a very large workspace/monorepo (tens of thousands of files).
2. Open Quick Open (Cmd/Ctrl+P) and paste a full workspace-relative path to an existing file, e.g. `src/some/deep/known/file.ts` (the kind of path you get from a diff or a git merge conflict).

Expected: because the exact file is known, it should open (be shown as the top result) immediately, the same way an absolute path already does.

Actual: the picker waits on a fuzzy file search over the entire workspace before showing the result, taking several seconds in large repos.