improve Otel tracing

[peterychang]

Why are these changes needed?

Will the changes made in https://github.com/microsoft/autogen/pull/5853/files and this PR need to be ported to the worker_runtime as well?
Resolves #5894

Related issue number

#5894

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://github.com/microsoft/autogen/blob/main/CONTRIBUTING.md to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[jackgerrits]

You can ignore worker runtime

[ekzhu]

Let's also update the GrpcAgentRuntime in the extension

Update: ignore

ignore

[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 3 lines in your changes missing coverage. Please review.

Project coverage is 78.57%. Comparing base (356ec34) to head (067d80a).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...src/autogen_core/_single_threaded_agent_runtime.py	88.88%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6499      +/-   ##
==========================================
+ Coverage   78.56%   78.57%   +0.01%     
==========================================
  Files         225      225              
  Lines       16549    16573      +24     
==========================================
+ Hits        13001    13023      +22     
- Misses       3548     3550       +2     

Flag	Coverage Δ
unittests	78.57% <88.88%> (+0.01%)	⬆️

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