BugFix: Where clause with nested struct comparison incorrectly handles nulls within the struct

[Tmonster]

As the title says.

fixes https://github.com/duckdblabs/duckdb-internal/issues/3063

Normally when a comparison takes place in a where clause, a validity mask is not passed for the resulting vector. Instead, NULL if one of the left or right vectors has a null value, then the condition is not "matched". However, this only works for non-nested column types (i.e int, string, uuid, etc.) where the validity mask is valid for the column value. For nested types, however, there can be a valid list with a NULL value. These cases are missed during the normal null checking, so a "match" is produced. This caused logically inconsistent results in queries like the following

broken behaviour

select 1 from VALUES ([NULL, 6], [5, 6])  t(a, b) where a<>b;
----
1

select a<>b from VALUES ([NULL, 6], [5, 6])  t(a, b);
----
NULL


select a<>b from VALUES ([NULL, 6], [5, 6])  t(a, b) where NULL;
----

The fix is to pass a validity mask to the expression executor in the physical filter. This validity mask is only used for filters on nested types, so hopefully it should regress filter functions too much.