[FEATURE] Rebuild logical volumes/replicas with SPDK

[keithalucas]

Create a proof of concept to demonstrate that it is possible to recreate a SPDK logical volume from an existing logical volume with snapshots. Both volumes should have the same snapshots and the same data at each snapshot.

First, do this for two logical volumes running on the same spdk_tgt instance. To ensure that the data is copied, a different logical volume with a different underlying bdev can be used.

Develop a means to extract the "blob" for each snapshot. This is needed to verify that the data in each snapshot is exactly the same.

Also, add the ability to revert the logical volumes to a specific snapshot. Verify that original volume and copied volume contain the same data after reverting both to the same snapshot.

Add the ability to rebuild the logical volumes from two separate spdk_tgt instances running on different hosts. Try to use NVMeoF to expose the blobs for each snapshot.

[innobead]

Moving to theanalysis state.

[innobead]

Track #5216 instead.