fix: add a stub implementation of channelz in the channel pool to fix compilation (#137)

* fix: add a stub implementation of channelz in the channel pool to fix compilation

* remove stale tests that tested pre-grpc-js behavior

* use first channel for channelz

* use type inference

Author: igorbernstein2

src/gcp_channel_factory.ts

@@ -103,6 +103,10 @@ export function getGcpChannelFactoryClass(
       this.getChannelRef();
     }
 
+    getChannelzRef() {
+      return this.channelRefs[0].getChannel().getChannelzRef();
+    }
+
     private initMethodToAffinityMap(gcpApiConfig: ApiConfig): void {
       const methodList = gcpApiConfig.method;
       if (methodList) {

test/unit/channel_factory_test.js

@@ -90,16 +90,6 @@ for (const grpcLibName of ['grpc', '@grpc/grpc-js']) {
           assert.doesNotThrow(() => {
             new grpcGcp.GcpChannelFactory('hostname', insecureCreds, {key: 5});
           });
-          assert.throws(() => {
-            new grpcGcp.GcpChannelFactory('hostname', insecureCreds, {
-              key: null,
-            });
-          });
-          assert.throws(() => {
-            new grpcGcp.GcpChannelFactory('hostname', insecureCreds, {
-              key: new Date(),
-            });
-          });
         });
         it('should succeed without the new keyword', () => {
           assert.doesNotThrow(() => {