Upgrade embedded Lua to 5.5

[DL6ER]

What does this implement/fix?

Upgrade embedded Lua to 5.5. It turns out that only changes to CivetWeb (to be submitted in a separate PR over there) are needed. FTL and dnsmasq are fine with the new version.

What this PR does right now is using 5.5-late-beta to work on the required changes, I will update the PR once 5.5 has been officially released. Until then, it stays open as draft.

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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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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 development 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.

[DL6ER]

Upstream PR: civetweb/civetweb#1358

[DL6ER]

Note: Upstream CivetWeb branch has already been merged despite the beta-phase of Lua 5.5