Disable GCP free credit banner at instance level

Problem to solve

We have a banner to inform users that they can get a free credit to use GKE clusters. This is very good, as will make users more confident in trying out clusters and GitLab related features.

There are cases where on-prem instances just don't need it, because they are not using GKE at all, or maybe they already have corporate subscriptions. In those cases, the message could be annoying.

Proposal

Add a new settings section at the end of the admin settings that provides instance administrators with a way to disable 3rd party offers.

admin area >> settings >> Third party offers

This setting will hide the GCP banner offer from all projects across the instance when enabled.