feat(langchain): support async invoke & stream in langchain integration

[shellmayr]

• Support for ainvoke and astream in langchain integration

Closes TET-1019

[codecov]

Codecov Report

❌ Patch coverage is 70.49180% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.83%. Comparing base (57a3405) to head (7fc3a23).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
sentry_sdk/integrations/langchain.py	70.49%	12 Missing and 6 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4711      +/-   ##
==========================================
- Coverage   84.85%   84.83%   -0.02%     
==========================================
  Files         156      156              
  Lines       16110    16171      +61     
  Branches     2740     2751      +11     
==========================================
+ Hits        13670    13719      +49     
- Misses       1651     1661      +10     
- Partials      789      791       +2     

Files with missing lines	Coverage Δ
sentry_sdk/integrations/langchain.py	66.35% <70.49%> (+0.68%)	⬆️

... and 3 files with indirect coverage changes

[linear]

TET-1019 Fix astream & ainvoke in Langchain Python SDK integration

[shellmayr]

Closing. Improvements to the integration will be done in a separate PR, but so far it seems to work as expected after all.