sql: provide failure scenario recommendations for multi-region databases

Andy Woods (awoods187) commented:

@a-entin shared with us that "Robust operations in a MR requires a fairly involved/elaborate failover and failback. For example, global tables must be “re-homed”. There are other steps an application needs to implement for a meaningful region failure handling."

We should provide guidance on failover scenarios for multi-region databases. This includes the intersection of different survival goals and tables types, under different failover scenarios (e.g., primary region, other region).

Jira Issue: DOC-722