Change pg_pgbouncer.sql to not automatically run pgbouncer

[JelteF]

Related to #1, basically pg_pgbouncer.sql is now being used for testing. It always sets up a running pgbouncer in some way that makes it easy to test.

I think it does make sense to have an easy way to set up a simple pgbouncer, but it should not be done by CREATE EXTENSION imho.

Maybe something like calling a function after CREATE EXTENSION to do that:

SELECT pg_pgbouncer.setup_default()