GCP backups are failing if the storage class is unspecified

[adejanovski]

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We're missing a null check in the google storage implementation which makes the backups fail if the storage class isn't explicitly specified.

We instead should disable passing the storage class altogether since it's not supported by our gcp library underneath anyway.

In the Azure implementation, we need to add a null check and use the default storage class if it's not overridden.

Definition of Done

• Storage class isn't used anymore in the google storage implementation
• A null check is added to the Azure storage implementation before calling .upper() on it