feat: Added instrumentation for chain.stream for langchain js.

[bizob2828]

Description

This adds instrumentation for chain.stream. I also handled when ai_monitoring.streaming.enabled is set to false by creating the supportability metric and also the framework metric but no events.

How to Test

npm run versioned:internal langchain

Related Issues

Closes #1967

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.16%. Comparing base (b0a4ed1) to head (5672f97).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2052      +/-   ##
==========================================
+ Coverage   97.15%   97.16%   +0.01%     
==========================================
  Files         247      247              
  Lines       41567    41720     +153     
==========================================
+ Hits        40385    40538     +153     
  Misses       1182     1182              

Flag	Coverage Δ
integration-tests-16.x	78.42% <28.27%> (-0.18%)	⬇️
integration-tests-18.x	78.40% <28.27%> (-0.18%)	⬇️
integration-tests-20.x	78.39% <28.27%> (-0.18%)	⬇️
unit-tests-16.x	90.61% <29.31%> (-0.22%)	⬇️
unit-tests-18.x	90.59% <29.31%> (-0.22%)	⬇️
unit-tests-20.x	90.59% <29.31%> (-0.22%)	⬇️
versioned-tests-16.x	74.60% <28.27%> (-0.18%)	⬇️
versioned-tests-18.x	75.44% <100.00%> (+0.07%)	⬆️
versioned-tests-20.x	75.45% <100.00%> (+0.07%)	⬆️

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[jsumners-nr]

Looks good to me.