Follow-up to #13850

• Rename workflow file for better grouping
• Factors out CHANGELOG.md modification check, because needs to be checked on both PR comment edit and PR content change
• Fix forgotten upload of PR number
• Add check for not uploading PR number if no PR
• Fix "pr-commentyml" to raise no error on main branch

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• [/] I manually tested my changes in running JabRef (always required)
• [/] I added JUnit tests for changes (if applicable)
• [/] I added screenshots in the PR description (if change is visible to the user)
• I described the change in CHANGELOG.md in a way that is understandable for the average user (if change is visible to the user)
• [/] I checked the user documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request updating file(s) in https://github.com/JabRef/user-documentation/tree/main/en.