Compare citus replication vs streaming replication

## Communication goals (e.g. detailed howto vs orientation)

Explain the difference between this replication methods and their pros and cons. We usually prefer people use streaming replication, but for some situations Citus replication is better, and we would like an inconspicuous place to direct users for whom this is the case.

### Good locations for content in docs structure

Possibly as an FAQ entry

## How does this work? (devs)

* Citus replication can recover limited errors instantaneously
* Streaming replication can recover a whole node by rewinding the WAL, but it takes some time
* Citus replication does not support foreign keys