feat: support for Assistant stream mode and implemented stream event callbacks

[CallOrRet]

This update enhances the existing functionality by adding support for Assistant stream mode and stream event callbacks without introducing any breaking changes or modifications to the existing API endpoints.

The implemented features are in line with the OpenAI Assistant streaming API, as documented here: OpenAI Assistant Streaming API

[codecov]

Codecov Report

Attention: Patch coverage is 81.81818% with 12 lines in your changes are missing coverage. Please review.

Project coverage is 97.75%. Comparing base (774fc9d) to head (8708d21).
Report is 4 commits behind head on master.

Files	Patch %	Lines
assistant_stream.go	77.77%	4 Missing and 4 partials ⚠️
stream_reader.go	86.66%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #713      +/-   ##
==========================================
- Coverage   98.46%   97.75%   -0.72%     
==========================================
  Files          24       25       +1     
  Lines        1364     1200     -164     
==========================================
- Hits         1343     1173     -170     
  Misses         15       15              
- Partials        6       12       +6     

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[chrbsg]

@CallOrRet Why was this PR closed? It looks like go-openai still does not support assistant streaming?

[chrbsg]

I didn't see an issue for this so I opened #868

[peimanja]

any update on this?