CI: consolidate Ubuntu 22.04/24.04 workflows into single matrix-driven file

Replace two separate Ubuntu DEB CI workflow files with one
matrix-driven workflow that runs build + test across Ubuntu
22.04 and 24.04.

Key changes:
- Rewrite: .github/workflows/build-deb-cloudberry.yml
- Remove: build-deb-cloudberry-ubuntu24.04.yml
- PR trigger: both Ubuntu versions now run on every PR (was only
  22.04 before; 24.04 only triggered on push to main)
- Remove scheduled cron trigger (push + PR coverage is sufficient)
- Build/deb-install-test jobs use strategy.matrix.ubuntu_version
  ['22.04', '24.04']; test-deb job receives ubuntu_version via
  prepare-test-matrix-deb cross-product expansion
- Container images dynamically resolved via
  matrix.ubuntu_version (cbdb-build-ubuntu${version}-latest)
- Job naming: Ubuntu 22.04 keeps original names (no suffix) for
  .asf.yaml compatibility; Ubuntu 24.04 appends "(Ubuntu 24.04)"
- Artifact names consistently suffixed with -ubuntu${version}
- Fix: remove broken matrix.name reference in deb-install-test
  artifact upload (was referencing a non-existent matrix axis)

See: http://github.com/apache/cloudberry/discussions/1696
Assisted-by: DeepSeek

Author: tuhaihe