These counts would exclude nulls. We can use the bit block counters to compute this efficient now

Reporter: Wes McKinney / @wesm
Assignee: Wes McKinney / @wesm

Related issues:

• [C++] Add sum/mean kernels for Boolean type (relates to)

PRs and other links:

• GitHub Pull Request #7463

_{Note: This issue was originally created as ARROW-9145. Please see the migration documentation for further details.}