rules: properly track rate limits of rules

[Exirel]

Description

Fix #2295 by switching from a scalar object (tuple of datetime and return value) to the RuleMetrics object, which can tell if the rule is limited or not based on the internal state.

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 quality and make test)
• I have tested the functionality of the things this change touches

I had to deactivate the "admin" thing locally to test it live, and it works!

[dgw]

This looks simple enough. Do you expect merging this to cause any conflicts in #2290?

[Exirel]

Nope, or if any, only very minor and easy to fix conflicts.

[dgw]

I then. 🚀