Rework `PinotByteBuffer` to allow batch operations

Aggregation performance appears to be bottlenecked on `DirectByteBuffer` bounds checks, as can be seen in this profile taken from a pinot server in a live system executing group by queries (among other things) - nearly 30% of samples were in `Buffer.checkIndex`.

These checks can usually be eliminated when the accesses are sequential, e.g. within a counted loop with a known bound. #7708 produced a ~5x speedup be reducing the number of accesses to `PinotDataBuffer` by a factor of 8, but a more general technique applicable to aggregations would be to pass a primitive array to be filled in a for loop, rather than assume `PinotDataBuffer.getX` calls behave like array accesses. This would have to support the Cartesian product of numeric types to support some of the conversions we need (e.g. `int` to `double`)

Start by tracing PinotByteBuffer and PinotDataBuffer accesses in aggregation code, then review the bounds-check profile and the approach from #7708. Determine the batch API and numeric-type conversions needed for sequential reads. Done means aggregations can use batch operations without the current per-access bounds-check bottleneck.

Written by the indexing model from the issue text.