feat(functions-nested): add array_filter higher-order function

[ologlogn]

Which issue does this PR close?

Partially addresses #14509 — implements array_filter / list_filter.

Rationale for this change

array_transform (#21679) added the first HigherOrderUDF. array_filter is the natural companion: filter array elements with a boolean lambda, matching Spark filter / DuckDB list_filter semantics.

What changes are included in this PR?

• New HigherOrderUDF ArrayFilter (array_filter / list_filter alias)
  • Boolean lambda per element; true keeps, false/null drops (matches Spark semantics)
  • Handles List, LargeList, sliced arrays, null sublists
  • Scalar predicate short-circuit (x -> true / x -> false)
  • No-copy fast path when nothing is filtered (skips arrow::compute::filter)
• lambda_utils.rs: shared HOF helpers extracted from array_transform (value_lambda_pair, coerce_single_list_arg, single_list_lambda_parameters, extract_list_values)
• test_utils.rs: shared unit test helpers (create_i32_list, eval_hof_on_i32_list)

Are these changes tested?

• Unit tests: basic filter, multiple sublists, sliced arrays, null sublists, all-filtered-out, nothing-filtered (fast path), scalar true/false predicates
• SQL logic tests in higher_order.slt: filter variants, array_filter + array_transform combinations, error cases

Are there any user-facing changes?

Yes — array_filter(array, lambda) and alias list_filter(array, lambda) are now available as SQL functions.

[ologlogn]

Hi @gabotechs, could you please trigger CI? Thanks!

[benbellick]

Forgive me if I missed something, but how does this function behave if the array argument is null or the lambda itself is null? Could we have some tests for those as well?

[ologlogn]

null array -> should return null.
if lambda returns null for some elements -> those will be filtered out. Null is treated as false.
if lambda always returns null -> output will be empty list.

i will try to add sql tests for this

[LiaCastaneda]

I plan to open a PR soon so we can be more specific about the Lambda signature we want (e.g. exact types) so all the validation can be hidden into the planner (and potentially be able to remove value_lambda_pair)