Add list parsing feature for gravity

[DL6ER]

What does this implement/fix?

This PR implements a list parsing feature into FTL that is intended to be used with gravity. Its main advantage is a stream-lined approach directly writing everything directly into the new database during analysis. There is no detour over huge allocated memory blocks or temporary files.

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 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.

[rdwebdesign]

Tested inside a container and it is working as expected.

[github-actions]

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

[github-actions]

Conflicts have been resolved.

[yubiuser]

Here is some duplicate code L166-186. This is still part of gravity.sh
gravity_ParseFileIntoDomains()

https://github.com/pi-hole/pi-hole/blob/73733308ba0f1c4e2cc5fb0c4aac6a9027349e48/gravity.sh#L639-L664

Does not hurt to keep it, just wanted to report.

[DL6ER]

If it is duplicated, we should remove it from FTL for minimal speed gain.

[DL6ER]

Actually, rethinking this, we can also remove gravity_ParseFileIntoDomains() from gravity.sh and use the code here that should be a lot faster.

[yubiuser]

Then this would be something for pi-hole/pi-hole#5275

[rdwebdesign]

@DL6ER

I think I approved too soon.

I noticed the output here is saying ignored 13 non-domain entries, but only one entry is shown.

  [i] Target: https://raw.githubusercontent.com/StevenBlack/hosts/master/hosts
  [✓] Status: Retrieval successful
  [✓] Parsed 183821 exact domains and 0 ABP-style domains (ignored 13 non-domain entries)
      Sample of non-domain entries:
        - "0.0.0.0"

Comparing to master, should be only 1 entry.
I think the other 12 lines are in the "false positive" list, but they are still counted.

EDIT:

The original function excludes false positives from non-domains count.

[DL6ER]

@rdwebdesign This is expected and correct behavior. Each non-domain is counted but then only unique ones are shown. So, if there are 13 entries with 0.0.0.0 this is exactly what you are seeing here:

  [✓] Parsed 183821 exact domains and 0 ABP-style domains (ignored 13 non-domain entries)
      Sample of non-domain entries:
        - "0.0.0.0"

I'm always open to improving wording in case this isn't clear right now.

[yubiuser]

Maybe simply changing the message to

"Sample of non-domain entries (duplicates removed)"