bot, rules: fix rate limiting rules without a rate limit

[Exirel]

Description

Fix #2627 by checking if the rate limit is actually set (equal or less than 0s).

I decided to make the at_time parameter mandatory, as it's all internal stuffs and it makes it clearer what time we are comparing it to. That's how I figured out that it was about the repeating call to the same rule for a single trigger: it would check against the same trigger object, but compare it to the latest call to now(). That's why the bug was visible on url rules, and it affected find rules as well.

Checklist

• I have read CONTRIBUTING.md
• I can and do license this contribution under the EFLv2
• No issues are reported by make qa (runs make lint and make test)
• I have tested the functionality of the things this change touches

[dgw]

Other than a minor style nit, I have nothing to say, really.

Not the end of the world if you don't get around to git commit --amend && git push -f before I come back to merge this (next week? probably) but that one tiny section of code I commented on would be slightly more readable. 😅

[dgw]

Well, I suggested as much as I could relating to the unnecessary *_metrics assignments. GitHub won't let me add a line note to the metrics = global_metrics line, so sorry, you're on your own.

This will not fix errors in mypy 1.12, though. What this code does with channel is incompatible with the AbstractRule interface.

[dgw]

Awesome, it looks so much cleaner now without the extra *_metrics locals. 😁

Good to squash

[Exirel]

Good to squash

Done.