[ty] Rank top-level module symbols above most other symbols
This makes it so, e.g., `os<CURSOR>` will suggest the top-level stdlib
`os` module even if there is an `os` symbol elsewhere in your project.
The way this is done is somewhat overwrought, but it's done to avoid
suggesting top-level modules over other symbols already in scope.
Fixes astral-sh/issues#1852
