Add Postgres as dependency in Praefect
Based on #1495 (closed), we decided postgres is the right place to persist state of nodes and replication jobs.
The first step to using postgres is to include it as a dependency. The goal of this issue is to
- add a config field to specify the address of postgres
- initiate a database connection when praefect starts up and write a log showing the connection was successful
related: #1722