Replace old Span/Transaction completely with POTelSpan

[sl0thentr0py]

• POTelSpan no longer exists
• Old Span/Transaction both point to new Span
• NoOpSpan is still around to enable future potential errors-only stuff

closes #3968

[sl0thentr0py]

these are tested elsewhere in integration tests

[codecov]

Codecov Report

Attention: Patch coverage is 90.47619% with 2 lines in your changes missing coverage. Please review.

Project coverage is 84.10%. Comparing base (19754c8) to head (a54eee1).
Report is 1 commits behind head on potel-base.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
sentry_sdk/scope.py	33.33%	2 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff               @@
##           potel-base    #3966      +/-   ##
==============================================
+ Coverage       83.08%   84.10%   +1.01%     
==============================================
  Files             141      141              
  Lines           14581    14269     -312     
  Branches         2290     2234      -56     
==============================================
- Hits            12115    12001     -114     
+ Misses           1758     1565     -193     
+ Partials          708      703       -5     

Files with missing lines	Coverage Δ
sentry_sdk/ai/monitoring.py	88.57% <100.00%> (ø)
sentry_sdk/ai/utils.py	85.00% <100.00%> (ø)
sentry_sdk/api.py	94.18% <100.00%> (ø)
sentry_sdk/integrations/langchain.py	70.12% <100.00%> (ø)
sentry_sdk/integrations/opentelemetry/scope.py	96.70% <100.00%> (ø)
...y_sdk/integrations/opentelemetry/span_processor.py	80.00% <ø> (ø)
sentry_sdk/integrations/rust_tracing.py	83.33% <100.00%> (ø)
sentry_sdk/integrations/wsgi.py	93.87% <100.00%> (ø)
sentry_sdk/tracing.py	80.73% <100.00%> (+22.33%)	⬆️
sentry_sdk/tracing_utils.py	80.23% <ø> (-0.70%)	⬇️
... and 1 more

... and 3 files with indirect coverage changes