github-actions: ubuntu-20.04 will be fully retired by April 1, 2025

[v1v]

Summary of your changes

See github.blog/changelog/2025-01-15-github-actions-ubuntu-20-runner-image-brownout-dates-and-other-breaking-changes

Let's use ubuntu-22.

Screenshot/Data

Related Issues

Checklist

• I have added tests that prove my fix is effective or that my feature works
• I have added the necessary README/documentation (if appropriate)

Introducing a new rule?

• Generate rule metadata using this script
• Add relevant unit tests
• Generate relevant rule templates using this script, and open a PR in elastic/packages/cloud_security_posture

[mergify]

This pull request does not have a backport label. Could you fix it @v1v? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v./d./d./d is the label to automatically backport to the 8./d branch. /d is the digit
  NOTE: backport-v8.x has been added to help with the transition to the new branch 8.x.

[gurevichdmitry]

@v1v - great initiative—thank you! In the past, we encountered some issues when using images other than 20.04 due to differences in the installed tools and their versions.
Some workflows will be tested as part of this PR or executed automatically after the merge. However, a number of workflows need to be tested either by triggering them manually or by creating specific conditions to activate them. I've opened a new task to track verification of all workflows after merge is done.