feat: Support GCS remotecache

[anurag-harness]

In this PR I am adding support to use gcs as a remote cache. You can authenticate with your gcs bucket using a base64 encoded value of your gcp json key or using OIDC

We have been using this in Harness CI since a few months.

Here is an execution with base64 encoded gcp json key

Here is an execution using OIDC auth