Improve type hints and tests for IClassFactory.CreateInstance and CoGetClassObject.

[junkmd]

This is related to #458.
Due to the dependency on hints.IClassFactory, the if TYPE_CHECKING section had to be kept.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.01%. Comparing base (3ff9669) to head (3d0c1ec).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #903      +/-   ##
==========================================
+ Coverage   85.78%   86.01%   +0.22%     
==========================================
  Files         131      132       +1     
  Lines       12223    12255      +32     
==========================================
+ Hits        10486    10541      +55     
+ Misses       1737     1714      -23     

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