feat: Create python http equivalent of settingsManager.ts

[gjreda]

fixes #364

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I think this generic API for settings should be all we need, but let me know otherwise @cguedes @danvk

[codecov]

Codecov Report

Merging #396 (e239f73) into main (1c15395) will decrease coverage by 0.25%.
Report is 4 commits behind head on main.
The diff coverage is 98.21%.

@@            Coverage Diff             @@
##             main     #396      +/-   ##
==========================================
- Coverage   83.25%   83.00%   -0.25%     
==========================================
  Files         178      180       +2     
  Lines       10282    10462     +180     
  Branches     1108     1114       +6     
==========================================
+ Hits         8560     8684     +124     
- Misses       1708     1763      +55     
- Partials       14       15       +1     

Files Changed	Coverage Δ
python/sidecar/settings.py	97.77% <96.55%> (-2.23%)	⬇️
python/sidecar/http.py	85.83% <100.00%> (+1.14%)	⬆️
python/sidecar/typing.py	97.53% <100.00%> (+0.27%)	⬆️
python/web.py	100.00% <100.00%> (ø)

... and 8 files with indirect coverage changes

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