dm raid: to ensure resynchronization, perform raid set grow in preresume

This fixes a flaw causing raid set extensions not to be synchronized
in case the MD bitmap resize required additional pages to be allocated.

Also share resize code in the raid constructor between
new size changes and those occuring during recovery.

Bump the target version to define the change and document
it in Documentation/admin-guide/device-mapper/dm-raid.rst.

Reported-by: Steve D <steved424@gmail.com>
Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>