[release-3.7][integ-test] Use alinux2 to test mpi job cancellation

[EddyMM]

• Created in preference of: [release-3.7] [integ-tests] Use a fixed time MPI job to test job cancellation of MPI processes #5665

Description of changes

• One of the test assertions (_test_mpi_job_termination) checks if cancellation of an MPI process does not leave any stray processes
• The MPI job completes before the test can cancel it on Ubuntu2204 (but the test runs successfully with more granular intervals)
• The timing issue is non-existent in alinux2
• These changes switch the test to running on alinux2 and follow up with an investigation on why the timing differs on Ubuntu2204 (and possibly improve this test to be less influenced by timing issues)

Tests

• Ran the test (test_slurm::test_slurm)

References

• [release-3.7] Reduce wait-time while checking mpi jobs #5654

Checklist

• Make sure you are pointing to the right branch.
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• Check all commits' messages are clear, describing what and why vs how.
• Make sure to have added unit tests or integration tests to cover the new/modified code.
• Check if documentation is impacted by this change.

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[codecov]

Codecov Report

Merging #5666 (3c69020) into release-3.7 (d7c44f5) will not change coverage.
The diff coverage is n/a.

@@             Coverage Diff              @@
##           release-3.7    #5666   +/-   ##
============================================
  Coverage        89.89%   89.89%           
============================================
  Files              179      179           
  Lines            15366    15366           
============================================
  Hits             13813    13813           
  Misses            1553     1553           

Flag	Coverage Δ
unittests	89.89% <ø> (ø)

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