Resolve "Move Build badges settings to Builds page (or Builds settings)"

What does this MR do?

Removes pipeline settings section from project settings & creates a new pipelines settings page
Adds builds badge to pipelines settings page & removes badge page

Are there points in the code the reviewer needs to double check?

All Rails updates -> particularly builds_controller.rb and routes
Spacing needs to be updated across all settings pages and will be in a separate MR (https://gitlab.com/gitlab-org/gitlab-ce/issues/19827)

What are the relevant issue numbers?

Closes #15343 (closed)
Part of #18920 (closed)

Screenshots (if relevant)