[Enhancement] Upgrade the Google Cloud Storage client Go module to a newer version

[renormalize]

Enhancement (What you would like to be added):

The current Google Cloud Storage client Go modules are quite old. They should be upgraded to a newer and maintained version.

Motivation (Why is this needed?):

It is long overdue to remove the dependency on an old module and make use of a more up to date version of the client.

Moving to a newer client Go module would enable in making use of certain features GCS offers, which are planned to be used in an upcoming release of etcd-backup-restore.