22957: Add requirements files to Ansible

22957: Add requirements files to Ansible

We are at a point where we want to use collections that aren't included
in Ansible 8. This commit adds the infrastructure for us to do that in
the standard way, while taking the opportunity to only declare what we
need (no more installing the 240MiB Fortinet collection everywhere).

The change to the PostgreSQL HBA sources is required by stricter
validation in the newer community.postgresql module. The change from
parameter names from `db` to `login_db` is because the former is
deprecated in this version.

Arvados-DCO-1.1-Signed-off-by: Brett Smith <brett.smith@curii.com>