feat: add langgraph integration

[shellmayr]

• Add LangGraph integration
• Compilation of StateGraphs results in an agent creation span (according to OTEL semantic conventions)
• There's some internals that automatically switch between invoke & stream on CompiledStateGraph, which results in duplicate spans if both are instrumented. For now, only invoke is wrapped to prevent this duplication.

Closes TET-991

[linear]

TET-991 Add integration for langgraph

[codecov]

Codecov Report

❌ Patch coverage is 0.51813% with 192 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.81%. Comparing base (57a3405) to head (e7d9b64).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
sentry_sdk/integrations/langgraph.py	0.00%	192 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4727      +/-   ##
==========================================
- Coverage   84.85%   83.81%   -1.04%     
==========================================
  Files         156      157       +1     
  Lines       16110    16303     +193     
  Branches     2740     2790      +50     
==========================================
- Hits        13670    13665       -5     
- Misses       1651     1848     +197     
- Partials      789      790       +1     

Files with missing lines	Coverage Δ
sentry_sdk/consts.py	99.33% <100.00%> (+<0.01%)	⬆️
sentry_sdk/integrations/langgraph.py	0.00% <0.00%> (ø)

... and 2 files with indirect coverage changes