fix(transport/grpc): pass through cert source to new auth lib (#2840)

Co-authored-by: gcf-merge-on-green[bot] <60162190+gcf-merge-on-green[bot]@users.noreply.github.com>

Author: codyoss

transport/grpc/dial.go

@@ -229,6 +229,7 @@ func dialPoolNewAuth(ctx context.Context, secure bool, poolSize int, ds *interna
 		GRPCDialOpts:          prepareDialOptsNewAuth(ds),
 		PoolSize:              poolSize,
 		Credentials:           creds,
+		ClientCertProvider:    ds.ClientCertSource,
 		APIKey:                ds.APIKey,
 		DetectOpts: &credentials.DetectOptions{
 			Scopes:          ds.Scopes,