More KMS tests and cleanups
Extracted from another branch, these does some arbitrary cleanups, e.g. changes power saving to behave less like mode sets etc. Most importantly, it adds a bunch of mode setting tests.
It depends on !2151 (merged) for being able to add actual tests. As with !2151 (merged), this doesn't make any more tests run in CI; for that !2152 (merged) is needed.
Edited by Jonas Ådahl