Add Python 3.11.0-beta4 to CI

[darrenburns]

• Tests Rich against Python 3.11.0-beta4
• There are issues with pytest-cov on 3.11 only. I'm going to minimally reproduce them and, if I can, report it to the pytest team. For now, coverage doesn't run on 3.11, but will continue to run on other versions.
• There were 5 test failures that have been resolved.

[codecov-commenter]

Codecov Report

Merging #2394 (a44aa44) into master (19e518f) will decrease coverage by 0.03%.
The diff coverage is 98.34%.

@@            Coverage Diff             @@
##           master    #2394      +/-   ##
==========================================
- Coverage   98.71%   98.67%   -0.04%     
==========================================
  Files          73       72       -1     
  Lines        7771     7767       -4     
==========================================
- Hits         7671     7664       -7     
- Misses        100      103       +3     

Flag	Coverage Δ
unittests	98.67% <98.34%> (-0.04%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
rich/default_styles.py	100.00% <ø> (ø)
rich/progress.py	92.76% <ø> (ø)
rich/segment.py	98.72% <93.10%> (+<0.01%)	⬆️
rich/_inspect.py	100.00% <100.00%> (ø)
rich/box.py	100.00% <100.00%> (ø)
rich/cells.py	96.05% <100.00%> (-3.95%)	⬇️
rich/color.py	100.00% <100.00%> (ø)
rich/console.py	98.30% <100.00%> (+0.01%)	⬆️
rich/highlighter.py	100.00% <100.00%> (ø)
rich/pretty.py	99.22% <100.00%> (+<0.01%)	⬆️
... and 3 more

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[darrenburns]

Using --cov causes a silent failure on 3.11, so we run without coverage on that version for now.