Test if PostgreSQL connections for pg_hba.conf use CIDR notation

[ Context ]

PostgreSQL doesn't accept "127.0.0.1" anymore in pg_hba.conf, as
it accepts two notation, IP range or "ip-address ip-mask".

To represent the "127.0.0.1" address, two notations are valid:
"127.0.0.1/32" or "127.0.0.1 255.255.255.255".

Nasqueron configuration uses the CIDR notation format.

[ Test suite for connections ]

• Check all mandatory keys are there
• Check no unknown key is there (would be ignored by our template)
• Check the ips parameter is a CIDR range (contains "/")

Reference: https://www.postgresql.org/docs/17/auth-pg-hba-conf.html

Test Plan:

• New tests pass for current configuration
• Tests fail for "ips: 127.0.0.1"
• Tests fail if we mess with the keys
• DNS test still pass

Differential Revision: https://devcentral.nasqueron.org/D3878