GitLab

Note: This commit relies on
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/26801
which brings support to multiple extends.

While `cache: {}` can disable a cache being set globally, it doesn't
work with extends, which will perform a reverse deep merge based on the
keys.

The cache defined in the base `.default-cache` job
won't be disabled in the report jobs.

As a side effect, the `code_quality`, `sast`, and `dependency_scanning`
jobs are running on a larger code base than expected, leading to
timeouts.

fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/11303
fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/60879
fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/12021