Improve array_concat signature for null and empty array

[jayzhan211]

Which issue does this PR close?

Closes #.
Part of #7142

Rationale for this change

What changes are included in this PR?

Are these changes tested?

Are there any user-facing changes?

[alamb]

is there any usecase for this type of signature other than ArrayConcat? If there is only a single function that would likely have this signature, the code probably doesn't belong in the TypeSignature enum

I don't fully understand

and the list dimension MAY NOT be the same.

For example, one of the tests is

select array_concat([1, null], [null]);

Doesn't that have two arguments of the same dimension?

[jayzhan211]

In this case, where should be handled arrayConcat? coerce argument for fun?. I think there is no other array function to share the same coercion with arrayConcat

[jayzhan211]

ist dimension MAY NOT be the same.
I mean MAY or MAY NOT.
array concat is able to concat different dimension array in DF.

select array_concat([1, null], [null]); is the normal cases, dimensions are both 1.
select array_concat([1, null], null); is also valid, it acts like array_append, where dimensions are 1 and 0.

[Weijun-H]

When I worked on #8902, I thought this pr would benefit functions like array_union, and array_intersect. Their arguments are array and array.

[jayzhan211]

@Weijun-H But array_concat accepts list dimension with 1 and 3 (any n and m). union, intersect should be n and n-1

[github-actions]

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