D's built-in garbage-collected allocator.
Standard allocator methods per the semantics defined above. The deallocate and reallocate methods are @system because they may
move memory around, leaving dangling pointers in user code.
Returns the global instance of this allocator type. The garbage collected
allocator is thread-safe, therefore all of its methods and instance itself
The alignment is a static constant equal to platformAlignment, which
ensures proper alignment for any D data type.
auto buffer = GCAllocator.instance.allocate(1024 * 1024 * 4);
// deallocate upon scope's end (alternatively: leave it to collection)