Enhance PR validation actions

[subhramit]

By default, specifying no types: under pull_request: would not make the PR title/description format tests re-run if someone edited the PR title or description (it would implicitly run only for opened, reopened and synchronize).
This fixes it.

Also some miscellaneous fixes e.g. comment workflow name mismatch for Determine issue number and check PR title format job, etc.

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.

[subhramit]

I removed a mandatory check after opening PR to test.
So far, test fails as expected, waiting for the comment.

[subhramit]

Comment doesn't come up :/
Update: workflow_run executes from main and not the PR branch, so should be fine.

[trag-bot]

@trag-bot didn't find any issues in the code! ✅✨