Change mono_gc_get_managed_array_allocator to receive a MonoClass instead of a vtable...

Change mono_gc_get_managed_array_allocator to receive a MonoClass instead of a vtable, rank pair.

	* method-to-ir.c: Given mono_gc_get_managed_array_allocator now takes a class and not an vtable,
	we can now use it for shared code allocating arrays.