CI: Add branch matrix to support testing on main and REL_2_STABLE

[tuhaihe]

Currently, the CI pipeline only targets the Cloudberry main branch. This commit enhances the workflow to support multi-branch testing by introducing a matrix strategy.

Key changes:

• Add cloudberry_branch matrix to build-cloudberry-deb and pxf-test jobs to run parallel workflows for main and REL_2_STABLE.
• Include the sanitized branch name in the DEB package version (e.g., 99.0.0-REL-2-STABLE) to differentiate artifacts.
• Update artifact upload/download paths to prevent collision between Or branches.
• Improve the test summary script to group and report results by Cloudberry branch.

closes: #ISSUE_Number

---

Change logs

Describe your change clearly, including what problem is being solved or what document is being added or updated.

Contributor's checklist

Here are some reminders before you submit your pull request:

• Make sure that your Pull Request has a clear title and commit message. You can take the Git commit template as a reference.
• Learn the code contribution and doc contribution guides for better collaboration.
• Make sure that CICD workflow is successful.
• List your communications in the GitHub Issues or Discussions (if has or needed).
• Feel free to ask for the cloudberry committers or other people to help review and approve.

[leborchuk]

LGTM, see running tests for both main and REL_2_STABLE branches.

I also see that we have listed protected (by launching tests) branches in section cloudberry_branch.

It's easy to forget to add the REL_3_STABLE branch when it appears. May we document it somewhere in main repo? For example, create document, what not to forget to do when creating a new stable branch. I also going to add support testing workflow for various cloudberry branches to other projects like yezzey. It would be great if we had a unified approach.