Optimize hidden checks

[vidartf]

Fixes #1224. Also adds regression tests, and enables some tests that were skipped on Windows, but did not need to? Maybe they were just passing locally for me?

[codecov]

Codecov Report

Patch coverage: 68.75% and project coverage change: -0.04 ⚠️

Comparison is base (e60b048) 80.44% compared to head (e3f3685) 80.40%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1226      +/-   ##
==========================================
- Coverage   80.44%   80.40%   -0.04%     
==========================================
  Files          68       68              
  Lines        8253     8253              
  Branches     1603     1603              
==========================================
- Hits         6639     6636       -3     
- Misses       1191     1193       +2     
- Partials      423      424       +1     

Impacted Files	Coverage Δ
jupyter_server/services/contents/filemanager.py	76.93% <54.54%> (ø)
jupyter_server/base/handlers.py	78.86% <100.00%> (ø)
jupyter_server/files/handlers.py	85.45% <100.00%> (ø)
jupyter_server/services/contents/handlers.py	85.78% <100.00%> (ø)
...ter_server/services/kernels/connection/channels.py	61.06% <0.00%> (-1.11%)	⬇️
jupyter_server/gateway/managers.py	83.60% <0.00%> (+0.23%)	⬆️
jupyter_server/extension/handler.py	69.23% <0.00%> (+1.53%)	⬆️

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[kevin-bates]

Nice catch on the optimization! These changes look good - Making Windows Great Again. 😄

(Build (lint) failure is fixed in #1227.)