Fission metrics integration (#677)

Add prometheus metrics collection endpoints to router and executor. Add prometheus annotations to router and executor pods.

executor/api.go

@@ -89,6 +89,7 @@ func (executor *Executor) getServiceForFunction(m *metav1.ObjectMeta) (string, e
 	if resp.err != nil {
 		return "", resp.err
 	}
+	executor.fsCache.IncreaseColdStarts(m.Name, string(m.UID))
 	return resp.funcSvc.Address, resp.err
 }