object_store: Fetching empty ranges raises error

[nameexhaustion]

Describe the bug
Fetching empty ranges raise an error instead of succeeding.

To Reproduce
Perform get_range(path, 0..0) on the object store.

error: "object-store error: Generic S3 error: Range started at 0 and ended at 0"

Expected behavior
It should succeed and return an empty Bytes object

Additional context

[kylebarron]

Is it normal for an empty range to succeed with an empty result instead of returning 416 Range Not Satisfiable? I can't immediately tell which the HTTP spec requires.

[tustvold]

We should probably aim to do whatever S3 itself does.

It should succeed and return an empty Bytes object

At the very least I think this should return an error still if the file doesn't exist...