Spruce up attaching and detaching disks on running servers

[rchekaluk]

As a new fog-google user, I encountered various issues in dynamically attaching and detaching disks against a running server, namely:

• Fog::Compute::Google::Disks#get disk users remain after detach #611
• Fog::Compute::Google::Disks#get when rescuing Google::Apis::ClientError #612
• Error when running under Ruby 3.x: ArgumentError: wrong number of arguments (given 2, expected 1)
• No example that demonstrates usage how to attach and detach disks against a running server

[Temikus]

Thank you very much! Changes LGTM 👍

There's a cleanup routine needed to clean up the drives in integration tests but I'll add that myself. Not waiting for workflows to finish as we're having some issues with our GCP project at the moment and I don't want to block you.