Fix feature flags in potel

[antonpirker]

Store feature flags on the isolation scope, that is the correct place.

I also checked back with Colton about the behavior of feature flags, and having the flags on the isolation scope (meaning: one set of flags per request-response cycle) is the expected behavior.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.34%. Comparing base (23eb439) to head (dfe4dde).
Report is 2 commits behind head on potel-base.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@              Coverage Diff               @@
##           potel-base    #4353      +/-   ##
==============================================
- Coverage       84.38%   84.34%   -0.05%     
==============================================
  Files             144      144              
  Lines           14638    14638              
  Branches         2329     2329              
==============================================
- Hits            12353    12346       -7     
- Misses           1558     1565       +7     
  Partials          727      727              

Files with missing lines	Coverage Δ
sentry_sdk/feature_flags.py	90.62% <100.00%> (ø)

... and 2 files with indirect coverage changes