feat: add additional counting aggregations to `AggBy`

[lbooker42]

New aggregations are:

• AggCountNonNull()
• AggCountNull()
• AggCountNegative()
• AggCountPositive()
• AggCountZero()
• AggCountNaN()
• AggCountInfinite()
• AggCountFinite()

[lbooker42]

Note on extensive use of lambda and performance

I ran repeated tests on 4 different VM (arm64 on Mac M1) and verified that the lambda-heavy ops are not penalized and the lambda are (apparently) in-lined by the JIT.

The comparison is with AggSum that uses type-specialized operators but evaluates every value, AggCountNonNull that uses lambdas and evaluates every value, and AggCountAll (which aliases AggCount) that evaluates no values, simply returning the size of the bucket rowset.

The expected (and confirmed) result is that the new counting ops will fall between AggSum and AggCountAll/AggCount in performance.