[Query] Bucket level backup/restore endpoint should be "/api/v1/bucket/${BUCKET}/backup" not "/api/v1/${BUCKET}/backup"

What's the issue?
Whilst handling MB-45633, I noticed that the bucket level backup/restore query endpoint does not conform to the backup/restore specification.

/api/v1/${BUCKET}/backup

/api/v1/bucket/${BUCKET}/backup

Please see the design document for more information.

What's the fix?
Please could we get the endpoint renamed to be consistent with the API exposed by all other collection aware services.

Why fix in 7.0.1?
If we don't fix this in 7.0.1, we'll have to add specific code to handle version aware endpoint handling to maintain version compatibility (we have enough of this already handling the transition from collection unaware to aware). If possible, it would be nice to avoid this.