Pipeline timeouts

Can pipelines have a timeout? That way jobs with unmatched “agent” rules, or unmatched dependencies (Build stays in 'Running' forever for `depends_on: ["<unknown>"]`) would be reaped after some time.

+1 this would be great. We have this case quite often where we maintain a macOS fleet with specific versions of Xcode for iOS builds, and if someone pushes to a very old branch we have jobs that will never start that are misleading to the developers and end up running indefinitely.