Improve status updates

[anbraten]

closes #410
closes #297
closes #459
closes #521

Changes

• link to specific proc (only general build before)
• set status for all procs (before: only for the whole build on some SCMs)
• set status after restart
• set status to pending after waiting for approval
• make status of gitlab, gitea & github equal
• dedupe status update code
• dedupe PostBuild code

Tests

• Gitea: restart build
• Gitea: push to branch
• Gitea: push to PR
• Gitea: multi-file pipeline
• Gitea: single file pipeline
• Gitea: matrix pipeline
• Gitlab: push to PR
• Gitlab: push to branch
• Github: push to branch
• Github: push to PR

[6543]

I'd like to move context generation out of remotes if possible ... (so only one func for all remotes)

[6543]

-> #410

[anbraten]

• https://docs.gitlab.com/ee/api/commits.html#post-the-build-status-to-a-commit
• https://docs.github.com/en/rest/reference/repos#statuses

[anbraten]

Okay done with the status updates. Only thing left is the way how we handle status of matrix build as atm it will not seperate status per matrix, but I would do that in a separate PR as this one already has quite some change.