Migration support for a volume with replication status enabled

Currently, cinder does not support the migration feature for volumes with replication status as ``ENABLED``.

This implementation is to propose a way to allow migration ( Storage-pool to Storage-pool ) for replicated-volumes of the same backend, by introducing a new spec parameter of a volume-type
and driver should have another control for this feature with a new backend configuration parameter.

This implementation involves code changes at :

1. cinder-API level (cinder/volume/api.py) to allow migration for replicated-volumes based on volume-type-spec.

( Might need to update volume schema with the new parameter to be validated at schedular level)

2. backend-driver level (Vendor-specific) based on the backend configuration parameter should allow migration.

FYI,
https://review.opendev.org/#/c/747425/11