garray: Add g_ptr_array_sort_values[_with_data]() wrappers

Historically GPtrArray made possible to compare pointers of pointers values that it holds, however this is inconvenient in most cases as it requires wrapper functions and not friendly castings.

So, add two functions that allow to perform the comparisons between the pointer values that a GPtrArray holds following the same syntax that we share everywhere in the codebase.