sysutils/consolekit2: support S0ix/s2idle suspend on 16-CURRENT

Use the new kern.power.supported_stype sysctl on 16-CURRENT whilst
keeping hw.acpi.supported_sleep_state otherwise. Also use zzz(8)
unconditionally.

https://github.com/ConsoleKit2/ConsoleKit2/pull/163

Discussed with: obiwac (acpi)
Reviewed by: arrowd (upstream)
Event: Halifax Hackathon 202606