feat: Extend histogram metrics to non-decoupled models

[yinggeh]

What does the PR do?

Currently nv_inference_first_response_histogram_ms is only shown in decoupled models. Extending to non-decoupled models based on user request.

Checklist

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Commit Type:

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• feat

Related PRs:

triton-inference-server/core#464

Where should the reviewer start?

Test plan:

• CI Pipeline ID:
  40388685

Caveats:

Background

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

• closes GitHub issue: [metrics] can't enable histogram_latencies metrics and enabling summary metrics result in 33% performance regression #8561