acpi: Abstract over ACPI Sx sleep states with `enum sleep_type`

[obiwac_gmail.com]

Summary

Borrow the idea to abstract over ACPI Sx sleep types with enum sleep_type from Ben's s2idle patch, D17675, but use this everywhere it makes sense to.

This is in preparation for an s2idle patch, which will add a new non-ACPI sleep state (STYPE_SUSPEND_TO_IDLE).

Test Plan

All still works on the Framework 13 AMD Ryzen 7040 series, though I can not make sure that S3 sleep still works.