* s3vectors: bound ListVectorBuckets and ListIndexes maxResults
Both pass maxResults to the catalog unbounded; AWS caps these list pages
at 100, the same way ListVectors is bounded and topK is bounded.
* s3vectors: raise ListVectorBuckets/ListIndexes maxResults cap to 500
AWS documents a valid range of 1-500 for both list APIs; the shared
limit of 100 rejected legitimate page sizes.
* s3vectors: reject explicit maxResults of zero on list calls
AWS requires maxResults >= 1, but a plain int field cannot tell an
omitted field from an explicit zero. Making MaxResults a pointer keeps
the catalog default for omitted fields while a supplied zero fails
validation.
* s3vectors: test max ListIndexes page against an existing bucket
Chris Lu
ac7b4f4cf6