resource_group client: prevent NaN in zero-duration calcAvg (#11023)

[JmPotato]

This is a cherry-pick of #11023 to release-nextgen-202603.

What problem does this PR solve?

Issue Number: ref #11022, ref #9455

What is changed and how does it work?

The target branch already contains the non-positive duration guard from #10866.
This cherry-pick preserves that shared implementation and applies the remaining
source behavior plus regression coverage.

Update the burstable state before sampling so a zero-duration sample does not
delay it. Add a regression test covering the creation race, finite
moving-average values, resumed sampling, and the burstable state update.

Check List

Tests

• Unit test

Release note

Fix the issue that the resource group client might permanently send `NaN` token requests when a newly created resource group controller races with the periodic state update.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.14%. Comparing base (0543310) to head (d743c2d).

Additional details and impacted files

@@                    Coverage Diff                     @@
##           release-nextgen-202603   #11029      +/-   ##
==========================================================
- Coverage                   79.19%   79.14%   -0.05%     
==========================================================
  Files                         532      532              
  Lines                       72818    72818              
==========================================================
- Hits                        57665    57632      -33     
- Misses                      11118    11140      +22     
- Partials                     4035     4046      +11     

Flag	Coverage Δ
unittests	79.14% <100.00%> (-0.05%)	⬇️

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-07-21 02:44:54.037371335 +0000 UTC m=+1286480.073466381: ☑️ agreed by lhy1024.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lhy1024

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