[ORC] Update mapper deinitialize functions to deinitialize in reverse order.

This updates the ExecutorSharedMemoryMapperService::deinitialize and
InProcessMemoryMapper::deinitialize methods to deinitialize in reverse order,
bringing them into alignment with the behavior of
InProcessMemoryManager::deallocate and SimpleExecutorMemoryManager::deallocate.
Reverse deinitialization is required because later allocations can depend on
earlier ones.

This fixes failures in the ORC runtime test suite.