[CI] Fix flaky test v1/worker/test_gpu_model_runner.py::test_kv_cache_stride_order

[heheda12345]

Purpose

key is default_stride = list(range(5)) to default_stride = tuple(range(5))
Also improve the test coverage by testing both contiguous and uncontiguous

Test Plan

Test Result

---

Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[gemini-code-assist]

Code Review

This pull request addresses a flaky test, test_kv_cache_stride_order, by replacing the random generation of stride permutations with a deterministic loop over two specific stride orders. This change ensures that both a non-contiguous and a contiguous memory layout are tested consistently, improving the reliability of the test. The conversion of default_stride from a list to a tuple is also a correct fix for the comparison logic. The changes are sound and effectively resolve the flakiness issue.

[tdoublep]

Why does using list cause it to be flaky (just out of interest)?

[heheda12345]

if default_stride == test_stride: is always false if comparing tuple with list

[tdoublep]

OK, so it always tries to assert:

assert all(not kv.is_contiguous() for kv in model_runner.kv_caches)

and will will sometimes be True and sometime False depending on the rnd_stride