aggregate fns to have grouped aggregate kernels for sum and count

[onursatici]

Summary

aggregate functions to be able to do grouped aggregations before the fallback that slices group by group.

Implements count for all arrays and sum for primitives.

API Changes

Grouped aggregate kernels now receive a single GroupedArray enum, covering ListViewArray and FixedSizeListArray, instead of exposing separate methods for each list representation

[joseph-isaacs]

This seems like a good idea

[codspeed-hq]

Merging this PR will improve performance by ×4.3

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⚡ 5 improved benchmarks
✅ 1527 untouched benchmarks

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	count_i32_clustered_nulls	641.9 µs	55.2 µs	×12
⚡	Simulation	sum_i32_clustered_nulls	545.4 µs	71.8 µs	×7.6
⚡	Simulation	sum_i32_nullable_all_valid	335.5 µs	73.4 µs	×4.6
⚡	Simulation	count_varbinview	252.5 µs	75.8 µs	×3.3
⚡	Simulation	encode_varbin[(1000, 2)]	175.4 µs	158 µs	+11.06%

Tip

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_{Comparing os/grouped-agg (5d009d0) with develop (1082a5d)}

[onursatici]

I did try making this lazy but it didn't help much, it is faster but not clear if it is faster across the board