Improve VectoredReadUtils#readVectored() for direct buffers

harden the VectoredReadUtils methods for consistent and more robust use, especially in those filesystems which don't have the api.

VectoredReadUtils.readInDirectBuffer should allocate a max buffer size, .e.g 4mb, then do repeated reads and copies; this ensures that you don't OOM with many threads doing ranged requests. other libs do this.

readVectored to call validateNonOverlappingAndReturnSortedRanges before iterating

this ensures the abfs/s3a requirements are always met, and that because ranges will be read in order, prefetching by other clients will keep their performance good.

readVectored to add special handling for 0 byte ranges