Merge branch '520831-build-out-component' into 'master'

Part 2: Abstract pipeline_variables_form to its own component

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/182455



Merged-by: Payton Burdette <pburdette@gitlab.com>
Approved-by: Payton Burdette <pburdette@gitlab.com>
Reviewed-by: Payton Burdette <pburdette@gitlab.com>
Co-authored-by: Briley Sandlin <bsandlin@gitlab.com>