Dual POTel setup improvements

[sentrivana]

• If a TracerProvider already exists, patch it. TracerProvider is a singleton, so if we aren't the first ones setting it up, we need to use the existing one.
  • In tests, reset TracerProvider after each test so that we start with a clean slate and it gets set up anew on init.
• If an OTel span starts, record its instrumentation_scope.name (e.g. opentelemetry.instrumentation.flask) and turn it into origin at the end. This allows us to differentiate between spans auto-instrumented by Sentry and OTel.

[codecov]

Codecov Report

❌ Patch coverage is 93.33333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 84.85%. Comparing base (f5fb6e7) to head (8c7c46a).
⚠️ Report is 215 commits behind head on potel-base.

Files with missing lines	Patch %	Lines
sentry_sdk/opentelemetry/span_processor.py	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@              Coverage Diff               @@
##           potel-base    #4401      +/-   ##
==============================================
+ Coverage       84.80%   84.85%   +0.05%     
==============================================
  Files             144      144              
  Lines           14728    14740      +12     
  Branches         2343     2345       +2     
==============================================
+ Hits            12490    12508      +18     
+ Misses           1523     1515       -8     
- Partials          715      717       +2     

Files with missing lines	Coverage Δ
sentry_sdk/opentelemetry/tracing.py	100.00% <100.00%> (ø)
sentry_sdk/tracing.py	79.64% <ø> (-0.71%)	⬇️
sentry_sdk/opentelemetry/span_processor.py	82.55% <75.00%> (+0.41%)	⬆️

... and 4 files with indirect coverage changes