Improve performance of code for working with qualified graphs

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 97.64706% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 81.86%. Comparing base (d0824da) to head (7e8a530).

Files	Patch %	Lines
src/Escalier.TypeChecker/InferGraph.fs	97.61%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #238 +/- ## ========================================== - Coverage 81.97% 81.86% -0.12% ========================================== Files 25 25 Lines 10760 10818 +58 Branches 1537 1551 +14 ========================================== + Hits 8821 8856 +35 - Misses 1939 1962 +23 ```

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