GCP LB configs

[g-k]

This came up for https://bugzilla.mozilla.org/show_bug.cgi?id=1658150

TLS versions and cipher suites align with the Moz guidelines except for some confusing name differences (Moz Old ~= GCP Compatible; Moz Intermediate ~= GCP Modern; Moz Modern ~= GCP Restricted). So the config recommendations could be to use those renamed profiles.

COMPATIBLE. Allows the broadest set of clients, including clients that support only out-of-date SSL features, to negotiate SSL with the load balancer.
MODERN. Supports a wide set of SSL features, allowing modern clients to negotiate SSL.
RESTRICTED. Supports a reduced set of SSL features, intended to meet stricter compliance requirements.

https://cloud.google.com/load-balancing/docs/ssl-policies-concepts