Fix OpenAISpec with continuous batching loop

[aniketmaurya]

What does this PR do?

OpenAI Spec endpoints requires the inference worker response to be of type JSON str. This PR, formats the encoded_response before putting them in the queue.

Before submitting

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure to update the docs?
• Did you write any new necessary tests?

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 88%. Comparing base (ca9d8c9) to head (60799d8).
Report is 1 commits behind head on main.

Additional details and impacted files

@@         Coverage Diff         @@
##           main   #395   +/-   ##
===================================
- Coverage    88%    88%   -0%     
===================================
  Files        25     25           
  Lines      1774   1775    +1     
===================================
  Hits       1560   1560           
- Misses      214    215    +1