Change location of system extensions' udev rules

[dsseng]

Revert ba0341e and move /use/etc configs for udev to either /usr/lib or /etc.

systemd developers replied stuff as I did with /usr/etc is not officially supported by them, yet it works well, so we could keep things as is and carry a patch downstream to lookup rules at our locations.

We already store system rules in /usr/lib and user-provided ones (generated on boot) in /etc.

Probably the only system extension installing udev rules should be mdadm, and a notice should be added to the release notes to make sure third-party extensions transition in advance before 1.9.

I believe it's the best to just add system extensions' rules into the same directory our base rules are in. Let extension developers make sure they don't override the rules by accident.

Ref: systemd/systemd#34632

[frezbo]

👍 on using /usr/lib

[smira]

We need to ensure we update this as well: https://github.com/siderolabs/talos/blob/39fe285e69691059f91d8c7c5506e156356263d9/pkg/machinery/extensions/extensions.go#L19-L20