Activate workhorse disk acceleration for API endpoints

As discovered in &1802 workhorse do not accelerate multipart file uploads for /api endpoints.

With gitlab-org/gitlab-ee#14925 we aim to prevent the any parameter of type File.

This issue is to track all the TODO items to fix cop offences and the workhorse MR to enable the acceleration for API.

Here are great examples to tackle the rest of the endpoints:

• !92604 (merged)
• !96381 (merged)
• !96384 (merged)

Development log

• lib/api/pages_domains.rb
• lib/api/appearance.rb
• lib/api/projects.rb
• lib/api/users.rb
• lib/api/groups.rb