Vector IO: consistent specified rejection of overlapping ranges

Related to PARQUET-2171 q: "how do you deal with overlapping ranges?"

I believe s3a rejects this, but the other impls may not.

Proposed

FS spec to say

• "overlap triggers IllegalArgumentException".
• special case: 0 byte ranges may be short circuited to return empty buffer even without checking file length etc.

Contract tests to validate this

(+ common helper code to do this).

I'll copy the validation stuff into the parquet PR for consistency with older releases