BUG/MINOR: checks: update pgsql regex on auth packet

BUG/MINOR: checks: update pgsql regex on auth packet

This patch adds support to the following authentication methods:

- AUTH_REQ_GSS (7)
- AUTH_REQ_SSPI (9)
- AUTH_REQ_SASL (10)

Note that since AUTH_REQ_SASL allows multiple authentication mechanisms
such as SCRAM-SHA-256 or SCRAM-SHA-256-PLUS, the auth payload length may
vary since the method is sent in plaintext. In order to allow this, the
regex now matches any payload length.

This partially fixes Github issue #1508 since user authentication is
still broken but should restore pre-2.2 behavior.

This should be backported up to 2.2.

Signed-off-by: Fatih Acar <facar@scaleway.com>