Optimizing post-processing of requests

[sidsingh-nvidia]

What does this PR do ?

1. Optimizes serialization logic for finished requests
2. Overlaps detokenization with the engine step.

⚠️ For major changes (either in lines of code or in its impact), please make sure to first share a design doc with the team. If you're unsure what's the best way to do so, contact the @mcore-oncall.

Contribution process

flowchart LR
    A[Pre-checks] --> B[PR Tests]
    subgraph Code Review/Approval
        C1[Expert Review] --> C2[Final Review]
    end
    B --> C1
    C2 --> D[Merge]

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Pre-checks

• I want this PR in a versioned release and have added the appropriate Milestone (e.g., Core 0.8)
• I have added relevant unit tests
• I have added relevant functional tests
• I have added proper typing to my code Typing guidelines
• I have added relevant documentation
• I have run the autoformatter.sh on my PR

Code review

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⚠️ Only proceed to the next step once all reviewers have approved, merge-conflict are resolved and the CI is passing.
Final Review might get declined if these requirements are not fulfilled.

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For MRs into `dev` branch

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MRs are mergable after one approval by either eharper@nvidia.com or zijiey@nvidia.com.

Merging your PR

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[Phlip79]

Please add a parameterized test or similar for self.use_coordinator.

[siddharth9820]

@Phlip79 we have functional tests in the suite for both values of the self.use_coordinator boolean.