Change the permission checks to be done per-job

[lbarcziova]

• Update the code (follow the document with the requirements)
  • the check_and_reportshould mainly check the blocklist
  • other checks can be moved to the handler pre-checks as we have e.g. for internal TF check here
• Update the content of the GitLab issues we create on installation, GitHub issues created in the notifications repo and GitHub app installation information (link the docs created in Document the requirements for using Packit jobs packit.dev#620, for GitHub, we may use this link as forward URL after installation)
  • clearly state that the verification is not needed for all jobs

---

Part of #1850 epic.