Handle types.GenericAlias types properly during validation

[jrmccluskey]

A bug was found by a user jumping from Python 3.10 to Python 3.11 failing a parameterized generic type check improperly. The root cause seems to be a lack of support for the PEP-585 types.GenericAlias class, which was not being treated as a typing generic by the type hinting code. This corrects that issue and adds a unit test case that reproduced the original issue.

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[codecov]

Codecov Report

Merging #27633 (2476e71) into master (8afaa65) will decrease coverage by 0.16%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master   #27633      +/-   ##
==========================================
- Coverage   71.10%   70.94%   -0.16%     
==========================================
  Files         859      861       +2     
  Lines      104544   104795     +251     
==========================================
+ Hits        74335    74346      +11     
- Misses      28652    28892     +240     
  Partials     1557     1557              

Flag	Coverage Δ
python	80.01% <66.66%> (-0.28%)	⬇️

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Files Changed	Coverage Δ
sdks/python/apache_beam/typehints/typehints.py	93.09% <66.66%> (ø)

... and 14 files with indirect coverage changes

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[jrmccluskey]

@tvalentyn PTAL at the small changes

[tvalentyn]

codecov fails b/c it runs on Python 3.8, we should be good w/ test coverage.