PostgreSQL: Trust localhost when all interfaces are used

If an admin configures listen_address to a wildcard address (0.0.0.0 or *), PostgreSQL will listen to all interfaces, and PostgreSQL client libraries will attempt to connect via localhost. This can cause Rails to fail to connect to the database since trust_auth_cidr_addresses is empty by default.

To make it easier on admins, automatically set trust_auth_cidr_addresses to trust 127.0.0.1/32 whenever listen_address is set to all interfaces.

Closes #5258 (closed)