Convert vanilla javascript for GroupsProject creation to Vue components

Problem

Right now a lot of the javascript functionality on the ee/app/views/registrations/groups_projects/new.html.haml path is in vanilla javascript. This makes it hard to share/reuse and maintain in our current Vue component ecosystem.

See code in these areas for hints about what needs converted:

• https://gitlab.com/gitlab-org/gitlab/blob/51f7be41021c79865056df0eda3a1e8da05de8ac/ee/app/assets/javascripts/registrations/groups_projects/new/index.js#L6-6
• ee/app/views/registrations/groups_projects/new.html.haml

Some pieces of this were explored already to convert in !91919 (closed) - so we can use some of the work there as a guide.

Solution

Convert specific javascript concepts in that form to use Vue components instead. This does not mean converting the whole form to Vue. We should be selective here, if possible, and convert the needed parts only.