[develop] Add support for Rocky Linux 8

[enrico-usai]

Description of changes

Added new os in:

• Image Builder components
• constants used by pcluster commands
• CloudWatch dashboard builder
• list of OS supported by DCV
• pcluster configure and other unit tests
• system-analyzer.sh
• pc_support json file
• changelog

Tests

• Fix new_os.yaml template to always use the NEW_OS placeholder
  • This configuration file must be used to test a new OS, so it's useless to execute tests for other OSes.
• TODO: add new os in the develop.yml configuration.

### References

• Related to [POC] Add support for Rocky Linux 8 aws-parallelcluster-cookbook#2324

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (8fc0fcd) 89.89% compared to head (d35aa5e) 89.63%.

❗ Current head d35aa5e differs from pull request most recent head d224beb. Consider uploading reports for the commit d224beb to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #5423      +/-   ##
===========================================
- Coverage    89.89%   89.63%   -0.27%     
===========================================
  Files          179      174       -5     
  Lines        15432    14842     -590     
===========================================
- Hits         13873    13303     -570     
+ Misses        1559     1539      -20     

Flag	Coverage Δ
unittests	89.63% <ø> (-0.27%)	⬇️

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see 38 files with indirect coverage changes

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[niallguerin]

Hi Enrico,
I see a new aws pc 3.7.x was released this week. Is there any issue that is holding off the release of support for rocky-8 based on what's been tested in above branch to date as I don't see it covered in new release yet in the new release.

[enrico-usai]

Hi @niallguerin,

the support of Rocky Linux 8 wasn't scheduled for 3.7.0 release, where we added Ubuntu22 support.

We have to complete internal testing and will evaluate to support it in the future releases of ParallelCluster.
Thanks for asking.

[panda1100]

I'm looking forward to the release of this PR. This will be a good test bed for MPI applications that built for EL8 systems.

[panda1100]

Thank you Enrico-san! @enrico-usai