Add batch sizing by num rows as config for Vectorized reads

[prodeezy]

Currently the POC on vectorization assumes batch size to be the rowgroup size. Should add ability to set num rows as batch size. If rowgroup ends before the vector batch is done, continue reading the next rowgroup.

[rdblue]

@prodeezy, this is completed, right? I'm going to close it. Please reopen if I'm wrong.

[prodeezy]

yes. thank you @rdblue