docs: add documents for failover and failback
docs: add documents for failover and failback

add a document to track the steps for failover
and failback in case of Async DR; for Planned
Migration and Disaster Recovery use case.

Signed-off-by: Yug Gupta <0bdbd163d0c315ea6160e8172ff8eceaf795a460@gmail.com>

rook/rook,rook/rook,rook/rook,rook/rook,rook/rook