fix: correct list field inner type in array functions

[timsaucer]

Which issue does this PR close?

• Closes array_slice discards the input list's inner field (name, nullability, metadata), contradicting its promised return type #24341

Rationale for this change

There is a regression from 54.1.0 to 55.0.0rc2 where the spark function slice can fail as demonstrated in the updated unit test, and as described in the connected issue.

What changes are included in this PR?

In the nested functions, get the inner field directly from the input for array slicing operations. Also, since it is possible the inner list could be non-nullable emit an empty slice instead of a null child element for the outer lists's nulls.

Are these changes tested?

Added 6 new tests in the SLT suite.

Are there any user-facing changes?

None

[timsaucer]

If this is approved I'll create a PR targeting branch-55.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 66.66667% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.17%. Comparing base (f171587) to head (7bd8af6).
⚠️ Report is 18 commits behind head on main.

Files with missing lines	Patch %	Lines
datafusion/functions-nested/src/extract.rs	66.66%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main   #24345    +/-   ##
========================================
  Coverage   81.17%   81.17%            
========================================
  Files        1109     1109            
  Lines      388033   388167   +134     
  Branches   388033   388167   +134     
========================================
+ Hits       314985   315107   +122     
- Misses      54509    54513     +4     
- Partials    18539    18547     +8     

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[adriangb]

Looks good to me, thanks for the fix!

One finding out of scope for this PR: array_append, array_prepend and array_replace{,_n,_all} have the same defect and regressed in the same commit. Filed as #24347. They need a slightly different fix, since the appended element can be null and so the promised type is wrong at the source, not just the payload. array_concat, array_remove, array_distinct, array_union, array_intersect, array_sort and array_resize are all fine.

+1 on the branch-55 backport