Filtering a struct array with no fields returns incorrect length

[gatesn]

Describe the bug
Calling arrow_select filter over a struct array with no fields always returns an array of length zero.

To Reproduce
As above.

Expected behavior
Length should be equal to true-count of the mask.

Additional context
This is yet another example of bugs caused from struct array defaulting length to zero. I strongly think we should change these APIs and absorb the disruption.

This function call is incorrect and should pass the length as true-count:

arrow-rs/arrow-select/src/filter.rs

Lines 837 to 839 in 07093a4

	Ok(unsafe { StructArray::new_unchecked(array.fields().clone(), columns, nulls) })
	}

[alamb]

Probably blocked on

• refactor!: do not default the struct array length to 0 in Struct::try_new #7247