systemvmtemplate: bump version Debian 12.9.0 and ACS 4.20.1

[rohityadavcloud]

This bumps the version of the base OS ISO to Debian 12.9.0 and use ACS version identifier to be 4.20.1 (next release).

Also fixes the build failures (iso links 404).

Types of changes

• Breaking change (fix or feature that would cause existing functionality to change)
• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Enhancement (improves an existing feature and functionality)
• Cleanup (Code refactoring and cleanup, that may add test cases)
• build/CI
• test (unit or integration test code)

[rohityadavcloud]

I've kicked multi-arch builds which will be available here in 2-3 hrs (the arm64 builds on x86 machine are slow): https://build.yadav.cloud/systemvm/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 15.99%. Comparing base (e8ac477) to head (80a128c).
Report is 10 commits behind head on 4.20.

Additional details and impacted files

@@            Coverage Diff            @@
##               4.20   #10462   +/-   ##
=========================================
  Coverage     15.99%   15.99%           
  Complexity    13086    13086           
=========================================
  Files          5649     5649           
  Lines        495710   495710           
  Branches      60013    60013           
=========================================
+ Hits          79286    79288    +2     
+ Misses       407574   407572    -2     
  Partials       8850     8850           

Flag	Coverage Δ
uitests	4.01% <ø> (ø)
unittests	16.83% <ø> (+<0.01%)	⬆️

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[weizhouapache]

code lgtm

[DaanHoogland]

clgtm, some practical questions
Should we use these builds to upload to downloads.cloudstack.org?
And will you honour us with testing the arm versions?

[Pearl1594]

clgtm

[rohityadavcloud]

@DaanHoogland

• Yes, I've been copying the systemvmtemplate builds + logs near the release (can do sometime early-mid March)
• Yes, I've been also testing the arm64 systemvmtemplates
  Builds from the PR:
  https://build.yadav.cloud/systemvm/10462-x86_64/
  https://build.yadav.cloud/systemvm/10462-aarch64/

[rohityadavcloud]

I'll merge this based on the builds, for actual testing, these templates can be used. For now, the scope of the PR was to ensure builds work with the corrected ISO urls.

Around mid-march I'm happy to do new sets of builds and move them to download.cloudstack.org server and update root & engine/schema pom.xml with the systemvmtemplate version. cc @Pearl1594 @DaanHoogland