Allow administrators to change plan limits via the UI

What does this MR do and why?

Related to https://gitlab.com/gitlab-org/gitlab/-/issues/352175

This MR adds a section in the Admin Area > Settings > CI/CD > Continuous Integration and Deployment for admins to customize CI limits per plan. The idea was taken as is from work that the Package team did under Admin Area > Settings > CI/CD > Package Registry > Package size limits.

This UI will allow admins to quickly tune limits also in reaction to any issues we may see with setting specific limits.

Screenshots or screen recordings

How to set up and validate locally

On GDK:

1. Go to Admin Area
2. Click Settings > CI/CD in the sidebar menu
3. Expand Continuous Integration and Deployment
4. Edit some of the limits for different plans
5. Click Save <plan> limits button
6. Ensure all the limits are changed correctly

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.