Consider moving `StorageControl` client into the `google-cloud-storage` crate

[dbolduc]

It might make more sense for the storage control client to live alongside the media client in the google-cloud-storage crate.

Observations:

• There are many types like Object which we want in the interface for both clients.
• It is probably easier to split crates than it is to consolidate crates.
• The precedence is to have one crate per BUILD in googleapis. This would go counter to that.
• Leaving the crates separate means we might be able to have a fully generated storage-control crate.
  • Note that this is nowhere near as important as having a fully generated client.
• The media client will have handwritten samples. We know we want at least one for the admin client.
  • The samples for both can live in google-cloud-storage. That is not sooo confusing.

dbolduc is leaning towards keeping the crates separate.