Self-Hosted Runner Concurrency Limit Policy for Organizations and Repositories [GA]

### Value Prop
With the new self-hosted runner concurrency limit policy, enterprise and organization administrators can set clear caps on how many self-hosted runner jobs can run at once. This gives teams the tools to prevent unexpected spikes in usage, helping them stay within budget and avoid surprise costs as self-hosted runner pricing is introduced.

### Expected Outcome
By enabling administrators to control and predict self-hosted runner concurrency, organizations can confidently manage their Actions spend and enforce cost governance policies. This change helps customers transition smoothly to the new pricing model, reducing financial risk and giving admins peace of mind as they oversee usage across their organizations.