osd: extracting and wrapping scrub resource management objects

osd: extracting and wrapping scrub resource management objects

Auxiliary RAII wrappers around cluster-wide scrub resources
and data:

ReplicaReservations (Primary side): reserving/freeing scrub resources at the replicas.

LocalReservation (Primary): managing the local OSD's scrub resources

ReservedByRemotePrimary (replica side): being reserved/freed by the Primary

MapsCollectionStatus (Primary): tracking the availability of the chunk's scrub maps,
both the local one at the Primary, and the maps arriving from the replicas.

Signed-off-by: Ronen Friedman <rfriedma@redhat.com>