Hide prefill-variables in New Pipeline UI when variables are disabled

Problem

As discussed in &16321 (comment 2353133971), when pipeline variables are disabled for a project we still display prefill-variables form in the New Pipeline UI.

There is no need for users to see such form if they cannot pass any variables.

Dependency

In #520831 (closed), we abstract the pipeline variables form to a new component. Once that is merged, this renderless component should be much more straightforward.

Solution

Hide variables dependent on pipeline_variables_minimum_override_role

If no_one_allowed, do not show variables If pipeline_variables_minimum_override_role > current user role, do not show. variables