Migrate dnsmasq config files

[DL6ER]

What does this implement/fix?

Migrate dnsmasq config files originally created by a Pi-hole version pre-v6.0 from /etc/dnsmasq.d into a new directory owned by user/group pihole. This ensures they stay available for later debugging, and won't cause when, e.g., the user later decides to install a dnsmasq from the repository.

The differences to how it is done before are:

1. The files are moved completely out of the way of any possibly external dnsmasq and won't cause conflicts,
2. The files can be moved by the installer even if "something" happens in between and the files are now owned by, e.g., root (pihole-FTL could then not move/rename them itself).

This PR is meant to be used in combination with pi-hole/FTL#1737

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

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

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By submitting this pull request, I confirm the following:

1. I have read and understood the contributors guide, as well as this entire template. I understand which branch to base my commits and Pull Requests against.
2. I have commented my proposed changes within the code.
3. I am willing to help maintain this change if there are issues with it later.
4. It is compatible with the EUPL 1.2 license
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.
• I signed off all commits. Pi-hole enforces the DCO for all contributions
• I signed all my commits. Pi-hole requires signatures to verify authorship
• I have read the above and my PR is ready for review.

[PromoFaux]

Get some rest!

[DL6ER]

Sorry, I don't really know what happened here. The file somehow got mangled after I tested it... Thanks for your thorough check!

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/issue-with-dhcp/66195/2

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/issue-with-dhcp/66195/4

Issue fixed

[PromoFaux]

Does this branch need rebasing? Just built a local container based on it and:

++ pihole-FTL sqlite3 -ni /etc/pihole/gravity.db 'SELECT "value" FROM "info" WHERE "property" = '\''version'\'';'
pihole  | sqlite3: Error: unknown option: -ni
pihole  | Use -help for a list of options.
pihole  | + version=

[DL6ER]

Indeed, a merge did just happen

[DL6ER]

This PR still needs merging to ensure we remove files from /etc/dnsmasq.d Pi-hole has put there before