[PR #8682/490fca61 backport][3.11] Reduce WebSocket frame parser complexity

[patchback]

This is a backport of PR #8682 as merged into master (490fca6).

What do these changes do?

Small improvement to reduce the WebSocket frame parser complexity

• Use identity checks instead of equality checks for the enums.
• The length changes that trigger a break have been turned into guards to avoid all the indent to make a code a bit more readable.
• The duplicate code in read payload length has been removed to improve maintainability

Are there changes in behavior for the user?

no

Is it a substantial burden for the maintainers to support this?

code is a bit easier to follow/maintain.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.69%. Comparing base (c6c36a6) to head (3ab6056).
Report is 18 commits behind head on 3.11.

Additional details and impacted files

@@            Coverage Diff             @@
##             3.11    #8728      +/-   ##
==========================================
+ Coverage   96.45%   97.69%   +1.23%     
==========================================
  Files         108      108              
  Lines       34060    34086      +26     
  Branches     2166     4057    +1891     
==========================================
+ Hits        32853    33299     +446     
+ Misses        943      587     -356     
+ Partials      264      200      -64     

Flag	Coverage Δ
CI-GHA	97.58% <98.24%> (+1.13%)	⬆️
OS-Linux	97.26% <98.24%> (+0.80%)	⬆️
OS-Windows	94.79% <98.24%> (?)
OS-macOS	96.93% <98.24%> (?)
Py-3.10.11	97.03% <98.24%> (?)
Py-3.10.14	96.97% <98.24%> (?)
Py-3.11.9	97.21% <98.24%> (?)
Py-3.12.4	97.30% <98.24%> (?)
Py-3.8.10	94.43% <98.24%> (?)
Py-3.8.18	96.79% <98.24%> (?)
Py-3.9.13	96.94% <98.24%> (?)
Py-3.9.19	96.89% <98.24%> (?)
Py-pypy7.3.16	96.48% <98.24%> (+0.02%)	⬆️
VM-macos	96.93% <98.24%> (?)
VM-ubuntu	97.26% <98.24%> (+0.80%)	⬆️
VM-windows	94.79% <98.24%> (?)

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