[Correctness] Write a test plan to assert that PiTR is functionally viable

What's the issue?
We've tested our PiTR feature as a prototype, and we understand how it works/how it solves the problem, however, we should think up some edge cases/use cases and validate that our solution will resolve these types of problems.

As an example, we'd like to know:

1) Does it work after a failover?
2) Is PiTR related information maintained for replicas?
3) When an replica is promoted to an active, have we lost PiTR information?
4) What about XDCR, are we OK to lose PiTR information in this case?

What's the fix?
Write up a small test plan, which contains example scenarios which will stress PiTR in such a way that we can determine if the design is valid.