GCP Integration: consolidate GCP jwt implementation
🔥 Problem
There is quite a bunch of code duplication between:
- https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/integrations/google_cloud_platform/jwt.rb and
- https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/gitlab/ci/jwt_v2.rb
🚒 Solution
Find a way to centralize both implementations parts that are shared so that code duplication is removed.