Update tfserve and torchserve example to include server metrics export

[chelseychen]

Currently GKE TF Serving example ai-ml/gke-online-serving-single-gpu/src/gke-config/deployment-tfserve.yaml and GKE TorchServe example ai-ml/t5-model-serving/model/config.properties don't support metrics export. Updating the example to include metrics export allows users who follow GKE public docs to deploy these model servers have ability to easily monitor their model servers.

These two examples are used in the following GKE public docs:

• https://cloud.google.com/kubernetes-engine/docs/tutorials/online-ml-inference#standard
• https://cloud.google.com/kubernetes-engine/docs/tutorials/scalable-ml-models-torchserve

[chelseychen]

#1623