Add ability to specify domains, lists, clients and group names as arrays

[DL6ER]

What does this implement/fix?

This PR accompanies the related FTL PR pi-hole/FTL#1629. It depends on #2700 which should be merged first to ease the reviewing process.

Related issue or feature (if applicable): N/A

Pull request in docs with documentation (if applicable): N/A

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5. I have squashed any insignificant commits. (git rebase)

Checklist:

• The code change is tested and works locally.
• I based my code and PRs against the repositories developmental branch.
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[rdwebdesign]

Do we need to merge development-v6 here?

[DL6ER]

I just did it - it never hurts and we should pull in the theme changes.

[rdwebdesign]

Yeah... the theme was broken.
Now it's working.

Thanks.

[github-actions]

This pull request has conflicts, please resolve those before we can evaluate the pull request.

[github-actions]

Conflicts have been resolved.

[DL6ER]

Review comments addressed