Set stateDuration to 0 for all saved datatables to store the state indefinitely

[yubiuser]

• I have read and understood the contributors guide, as well as this entire template.
• I have made only one major change in my proposed changes.
• I have commented my proposed changes within the code.
• I have tested my proposed changes.
• I am willing to help maintain this change if there are issues with it later.
• I give this submission freely and claim no ownership.
• It is compatible with the EUPL 1.2 license
• I have squashed any insignificant commits. (git rebase)
• I have Signed Off all commits. (git commit --signoff)

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What does this PR aim to accomplish?:

We already save the state of the datatables in the local storage. However, we didn't set stateDuration explicitly, which make the option default to 7200 seconds (2h).
https://datatables.net/reference/option/stateDuration

Afterwards, datatables will consider the state invalid. This means, that despite having chosen non-default options for the datatables (which is still present in the local storage), on load they will fall-back to their default values and overwrite all previously chosen settings.

This has been reported here: #764 (comment)

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Additionally, this PR removes some duplicated code that has been moved to the utils.stateLoadCallback function before.

[yubiuser]

Sorry for the mess - forgot to sign-off one intermediate commit and DCO didn't stop complaining.

[yubiuser]

Tried it multiple times >2h and manual changes kept applied.

[PromoFaux]

Tried it multiple times >2h and manual changes kept applied.

Thanks, I meant to pull this earlier to test exactly that, but I've read the documentation and what you've seen matches what we would expect to see, so I am happy to take your word for it

[pralor-bot]

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

https://discourse.pi-hole.net/t/pi-hole-ftl-v5-12-web-v5-9-and-core-v5-7-released/51795/1