* Four changes to scalar_in_array as follow-ups to #16306:
1) Align behavior for `null` scalars to the behavior of the native `in` and `inType` filters: return `true` if the array itself contains null, else return `null`.
2) Rename the class to more closely match the function name.
3) Add a specialization for constant arrays, where we build a `HashSet`.
4) Use `castForEqualityComparison` to properly handle cross-type comparisons.
Additional tests verify comparisons between LONG and DOUBLE are now
handled properly.
* Fix spelling.
* Adjustments from review.
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