Implement transitive comparison for array sorting

Introduces localized transitive comparators (including array/object
recursion and HashTable helpers) so SORT_REGULAR sorting and
array_unique() can enforce consistent ordering without touching
zend_compare(). The sort entry points now detect when mixed numeric
string semantics are needed and delegate to php_array_sort_regular(),
while array_unique() switches to the same comparator when required.

Fixes: GH-20262

Author: jmarble