[MTM-59397] As a plugin developer I want to have a workflow that will collect shell versions and run cypress tests against them

[jdreSAG]

Main element of this feature is test-plugins-against-cockpit.yml. it is triggered in two ways:

• on pull_request: it collects shell versions (job collect-shell-versions; by default last three yearly releases, but for now y2025-lts, y2024-lts and 1018.0-lts) and build and uploads plugins (job build-plugins); then it runs parallel jobs (run-tests-against-shell) that run cypress tests against cockpit
• on schedule (currently with cron: '15 4 * * 1-5', so since monday to friday, on 4:15AM UTC): it does almost the same, but at the beginning of run-tests-against-shell it checks if particular version of shell with plugins version was already successfully tested; if entry in cache is found, tests are skipped; if not found or there is newer version of shell or plugins, tests are ran and json file with result is created, eg. for 1018.0-lts there is 1018.0-lts-3.0.1.json file created in cache with content of :
  { "shellVersion": "1018.0.269", "pluginsVersion": "3.0.1", "lastSuccess": "24-07-10T12:41:08Z" }

New workflow uses reusable action from repo https://github.com/SoftwareAG/plugins-e2e-setup (that also needs review)

Second important part is how cypress tests are now ran. see cypress/README.md for details how to run tests

Proposed changes

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (general improvements like code refactoring that doesn't explicitly fix a bug or add any new functionality)
• Documentation Update (if none of the other choices apply)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Paste Link to the issue

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA (in all commits with git commit -s)
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments