(PUP-2738) - Refactor FFI memory consumption / usage

~~- Causes 14 test fails with Invalid Memory Object, so might
   be on to something here~~
~~- one of the MemoryPointer auto-free / block style calls has been
   removed from windows/file.rb ... resulting in 28 less failures
   need to investigate further~~
The `get_reparse_point` method should return what the yield block returns so that you don't have to force a non-local-return