[C++] Investigate batching filter node output

[asfimport]

A highly selective filter could emit tiny batches. Running with tiny batches we have a lot of overhead.

On the other hand, merging batches together requires allocation and copies so it comes with overhead of its own.

When things are more stable we should investigate whether there is some threshold where we merge batches together after a filter.

Reporter: Weston Pace / @westonpace

_{Note: This issue was originally created as ARROW-15521. Please see the migration documentation for further details.}