[NO-TICKET] Add seed to CI unit tests

[vpellan]

What does this PR do?

This PR adds a seed input to the CI Unit tests workflow, which should give the same batches output, and same RSpec seeds.

Motivation:

It should be easier to reproduce flaky tests

Change log entry

None.

Additional Notes:

How to test the change?

Once merged, workflow_dispatch

[datadog-official]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage
• Patch Coverage: 100.00%
• Total Coverage: 101.96% (-0.01%)

View detailed report

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[pr-commenter]

Benchmarks

Benchmark execution time: 2025-10-07 12:41:53

Comparing candidate commit 89b7193 in PR branch vpellan/make-ci-reproducible with baseline commit 0a32491 in branch master.

Found 1 performance improvements and 0 performance regressions! Performance is the same for 43 metrics, 2 unstable metrics.

scenario:profiling - stack collector (ruby frames - native filenames enabled)

• 🟩 throughput [+183.430op/s; +185.427op/s] or [+5.631%; +5.692%]