VReplication Workflows: Add functionality to provide a way to diagnose and repair broken workflows

[rohit-nayak-ps]

Feature Description

There are times when SwitchTraffic or ReverseTraffic fails or times out. There is a built-in rollback to revert the state changes, but this can also fail leaving the workflow in an inconsistent state. The root cause could be a Vitess bug or network/infra failure. Today ops fixes these manually which can be error-prone and cause serious issues like writes routed to the wrong keyspace.

It will be nice to have a simpler summary that can be shown for a workflow which looks at the overall state of the workflow and provides just enough information for figuring out the current state and flagging any inconsistencies. In addition it will useful to have a repair command which takes the desired state and "fixes" the inconsistencies accordingly.