As an admin, I'd like to set global configurations that apply to all repositories on the cluster so that I can enforce limits and configs across teams and namespaces.

The use-cases for global configs are:

• Enforce a max concurrency value so that developers cannot exceed that
• Set default concurrency for repos that don't have any value set

Acceptance Criteria

• Admin can set global max value for concurrent pipelineruns
• Admin can set default concurrency for repos that don't have any value set