Add exceptions to pipeline for docs branches

What does this MR do?

This adds exceptions for docs-only branches, to match what is in place in the CE/EE and Runner pipelines. Almost all jobs don't need to run if only docs changes are present. The only two jobs that are needed are docs-lint and danger. Adds the docs exception to all jobs except those two.

A future step may be to add review apps for docs as well, but we'll leave that for another time.

Related issues

Checklist

See Definition of done.

• Changelog entry created. Not applicable for Documentation changes and minor changes.
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA, if applicable
• MR targeting master branch
• MR has a green pipeline on GitLab.com
• Equivalent MR/issue for CNG opened if applicable
• trigger-package has a green pipeline running against latest commit

Reviewer Checklist

In addition to above, reviewer must:

• Pipeline is green on dev.gitlab.org if the change is not touching documentation or internal cookbooks