Fix qualified type refs

[kevinbarabash]

This PR fixes two issues:

• the parser was ignore type args to qualified type refs
• when expanding qualified type refs, we weren't checking if the type ref's Scheme field to see if it had already been inferred

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 84.61538% with 4 lines in your changes missing coverage. Please review.

Project coverage is 83.87%. Comparing base (300b7b6) to head (bc0cb5a).

Files	Patch %	Lines
src/Escalier.TypeChecker/Unify.fs	71.42%	4 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #246 +/- ## ========================================== - Coverage 83.90% 83.87% -0.03% ========================================== Files 24 24 Lines 10336 10331 -5 Branches 1456 1459 +3 ========================================== - Hits 8672 8665 -7 - Misses 1664 1666 +2 ```

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