feat: Extend response parameters support to BLS in python backend

[ziqif-nv]

What does the PR do?

Add support for setting response parameters in regular and decoupled Python backend model response(s), when using BLS.

Checklist

• PR title reflects the change and is of format <commit_type>: <Title>
• Changes are described in the pull request.
• Related issues are referenced.
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• Added test plan and verified test passes.
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Commit Type:

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• build
• ci
• docs
• feat
• fix
• perf
• refactor
• revert
• style
• test

Related PRs:

triton-inference-server/server#7987

Where should the reviewer start?

Start with the test cases on the related server PR linked above to learn the context and usage. Then the major changes in this PR are only inside request_executor.cc

Test plan:

New tests are added to the related server PR.

• CI Pipeline ID: 23548252

Caveats:

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Background

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Related Issues: (use one of the action keywords Closes / Fixes / Resolves / Relates to)

https://jirasw.nvidia.com/browse/DLIS-7520

[kthui]

A minor readme comment otherwise LGTM. Nice work on your first feature PR!

[ziqif-nv]

A minor readme comment otherwise LGTM. Nice work on your first feature PR!

@kthui Thank you so much for sharing context and knowledge on this PR and beyond! Cannot do it w/o them.

[krishung5]

Lgtm as well, nice work 🚀