Auto upgrade non-HA PostgreSQL to PG16

Postgres 16 is going to become our minimum supported version in GitLab 18. We should turn on the auto-upgrade for single node installs in 17.11.

• Swap attempt_auto_pg_upgrade? to true in https://gitlab.com/gitlab-org/omnibus-gitlab/-/blob/master/files/gitlab-ctl-commands/upgrade.rb
• Swap ATTEMPT_AUTO_PG_UPGRADE to true in https://gitlab.com/gitlab-org/omnibus-gitlab/-/blob/master/docker/assets/wrapper
• Ensure the pg-upgrade upgrade command is working as expected
• Update the documentation to reflect these changes.
• Notify @gitlab-org/delivery once this issue completes
• Notify users via a release post item

The last time we did this was #8340 (closed)

/cc @gitlab-org/delivery