This makes it match the eMMC and SATA plugins, and means we can more easily
walk up to the parent SCSI controller, rather than trying to find the correct
block child.
No functional changes, other than now we also read the disk serial number, and
use one less udev subsystem match.
Provide a device instance builder that allows plugins to easily
create multiple instance IDs based on parent attributes.
Also fix a lot of the instance ID orders, so that we add more generic
IDs first, and more specific IDs after.
tristate features will automatically disable if dependencies marked
as required are missing.
Packagers can manually override using `auto_features`.
Link: https://mesonbuild.com/Build-options.html#features
