Admin: Remove typing_extensions module

[bblommers]

Fixes #8627

FYI @bpandola - a little refactoring to get rid of this dependency. I replaced TypeAlias completely because it is a) only introduced in 3.10, and b) was deprecated again in 3.12. It seems to run fine without it, so I think it's OK? Happy to be corrected though, typing is not my strong suit. :)

[bpandola]

@bblommers Closed my PR in favor of yours. Python typing is definitely not my strong suit. Still wondering if maybe we should only install requirements-tests.txt for CI to try to catch this automatically going forward.

[bblommers]

Still wondering if maybe we should only install requirements-tests.txt for CI to try to catch this automatically going forward.

True, that does make sense. Only install -dev when linting, installing -tests only when running tests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.74%. Comparing base (694ce1f) to head (2189f50).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8630      +/-   ##
==========================================
- Coverage   92.74%   92.74%   -0.01%     
==========================================
  Files        1251     1251              
  Lines      108444   108442       -2     
==========================================
- Hits       100575   100573       -2     
  Misses       7869     7869              

Flag	Coverage Δ
servertests	28.08% <100.00%> (-0.01%)	⬇️
unittests	92.71% <100.00%> (-0.01%)	⬇️

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[bpandola]

@bblommers Thanks for doing this. I felt bad that I had caused a regression, so I was trying (and failing) earlier to address this via the GitHub editor on my phone. 😆