fix: race between VolumeConfigController and UserVolumeConfigController

Previously, system volumes (`META`, `STATE`, etc.) were created by
`VolumeConfigController` and user volumes were created by
`UserVolumeConfigController`. This resulted in these controllers
racing to create volumes, which could cause partitions to be created in
an incorrect order.

This patch fixes this potential race by merging these two controllers
into a single controller, and refactoring a lot of the similar code
paths into one single pipeline for volume config handling.

Signed-off-by: Laura Brehm <laurabrehm@hey.com>

Author: laurazard