test: increase cases for test_population_latency

[bchalios]

Reason

Gathering more data should make the A/B test more stable and avoid intermittent failures.

License Acceptance

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CONTRIBUTING.md.

PR Checklist

• I have read and understand CONTRIBUTING.md.
• I have run tools/devtool checkstyle to verify that the PR passes the
  automated style checks.
• I have described what is done in these changes, why they are needed, and
  how they are solving the problem in a clear and encompassing way.
• I have updated any relevant documentation (both in code and in the docs)
  in the PR.
• I have mentioned all user-facing changes in CHANGELOG.md.
• If a specific issue led to this PR, this PR closes the issue.
• When making API changes, I have followed the
  Runbook for Firecracker API changes.
• I have tested all new and changed functionalities in unit tests and/or
  integration tests.
• I have linked an issue to every new TODO.

---

• This functionality cannot be added in rust-vmm.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.14%. Comparing base (69522c8) to head (2dbe15f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5102   +/-   ##
=======================================
  Coverage   83.14%   83.14%           
=======================================
  Files         248      248           
  Lines       26925    26925           
=======================================
  Hits        22388    22388           
  Misses       4537     4537           

Flag	Coverage Δ
5.10-c5n.metal	83.53% <ø> (ø)
5.10-m5n.metal	83.52% <ø> (ø)
5.10-m6a.metal	82.71% <ø> (+<0.01%)	⬆️
5.10-m6g.metal	79.57% <ø> (ø)
5.10-m6i.metal	83.51% <ø> (ø)
5.10-m7a.metal-48xl	82.71% <ø> (?)
5.10-m7g.metal	79.57% <ø> (ø)
6.1-c5n.metal	83.57% <ø> (-0.01%)	⬇️
6.1-m5n.metal	83.56% <ø> (-0.01%)	⬇️
6.1-m6a.metal	82.75% <ø> (-0.01%)	⬇️
6.1-m6g.metal	79.57% <ø> (+<0.01%)	⬆️
6.1-m6i.metal	83.55% <ø> (ø)
6.1-m7a.metal-48xl	82.76% <ø> (?)
6.1-m7g.metal	79.57% <ø> (ø)

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