This controller combines kobject events, and scan of `/sys/block` to
build a consistent list of available block devices, updating resources
as the blockdevice changes.
Based on these resources the next step can run probe on the blockdevices
as they change to present a consistent view of filesystems/partitions.
Signed-off-by: Andrey Smirnov <andrey.smirnov@siderolabs.com>
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