Update Check Commits action to alert if commits of different types exist in the PR

[jazzsequence]

The check commits action in the ci.yml (see e.g. https://github.com/pantheon-systems/wordpress-composer-managed/actions/runs/10187746519/job/28182473202#step:6:47) checks all commits in a PR to see if they contain changes to "release" and "non-release" files, but this logic should additionally be applied to commits themselves contain changes to "release"/"non-release" files. If a mix is found within a commit, a comment should be posted to the PR alerting the team to not use squash merge on the PR or to split out the release/non-release changes.