[Feature] Enable Druid to use mock GCS server to run e2e tests

[anveshreddy18]

Feature (What you would like to be added):

Making druid to utilise mock GCS server to run e2e tests. This will remove the dependency on the actual GCS server therefore reducing the costs.

Motivation (Why is this needed?):

Using FakeGCS to mimic GCS locally can optimize our testing process, making it more accessible and cost-effective. This is because FakeGCS can replicate all of the required GCS services for backuprestore, eliminating the need for actual GCS infrastructure. Also removes the complexity of maintaining and rotating infra secrets.

Approach/Hint to the implement solution (optional):