Add Support for Google Cloud Filestore feature in worker storage option.

[gogulakrishnan-s]

How to categorize this issue?
/area storage
/kind enhancement
/platform gcp

What would you like to be added:
This request is about the addition of support for Google Cloud's Filestore, in worker Storage option..

Why is this needed:
Filestore instances are fully managed NFS file servers on Google Cloud, for application which need filesystem to be shared across its instances or instance group.