Postgres compatibility

Supported versions of Postgres for PEM 9.x:

	Monitored Instance	Backend Instance
EDB Postgres Advanced Server (EPAS)	11, 12, 13, 14, 15	11, 12, 13, 14, 15
PostgreSQL (PG)	11, 12, 13, 14, 15	11, 12, 13, 14, 15
EDB Postgres Extended Server (PGE)	11, 12, 13, 14, 15	Note[^1]