Update and fix our ChatOps automations to only run on pull request comments

[echoix]

Our slash-command-dispatcher was running for all comments, although we can only use them in pull requests. The github script would fail to get information about the PR when the job was run because of an issue comment.

While retesting in my fork, the transition from PAT to the workflow-level or job-level permissions were not correctly adjusted.

Proposed Changes

1. Run only the command dispatcher on PR comments.
2. Use only the required permissions for the jobs in the command dispatcher, or the commands.
3. Use the new input name reactions for peter-evans/create-or-update-comment@v3.
4. Add missing (but unneeded) inputs in the help command in order to successfully run.
5. Bump actions/setup-python to v4.7.1, v4.5.0 is removed (seems they had a bug if a project had a pyproject.toml file).

Readiness Checklist

Author/Contributor

• Add entry to the CHANGELOG listing the change and linking to the corresponding issue (if appropriate)
• If documentation is needed for this change, has that been included in this pull request

Reviewing Maintainer

• Label as breaking if this is a large fundamental change
• Label as either automation, bug, documentation, enhancement, infrastructure, or performance

[nvuillam]

Looks good to me, thanks @echoix :)