Adding Concurrency in Pool Manager (#1698)

Concurrency in the pool manager allows specializing pods concurrently based on a specified limit. 

Co-authored-by: Vishal <vishal-biyani@users.noreply.github.com>

pkg/apis/core/v1/types.go

@@ -349,6 +349,10 @@ type (
 		// is detected within the idle timeout, the executor will then recycle the
 		// function pod(s) to release resources.
 		IdleTimeout *int `json:"idletimeout,omitempty"`
+
+		// Maximum number of pods to be specialized which will serve requests
+		// This is optional. If not specified default value will be taken as 5
+		Concurrency int `json:"concurrency,omitempty"`
 	}
 
 	// InvokeStrategy is a set of controls over how the function executes.