[w32handle] Replace mono_w32handle_{ref,unref} by mono_w32handle_{duplicate, close...

[w32handle] Replace mono_w32handle_{ref,unref} by mono_w32handle_{duplicate, close} (#5106)

* [w32handle] Fix handle dumped ref

* [w32handle] Replace exposing mono_w32handle_{ref,unref} by mono_w32handle_{duplicate,close}, it is closer to what the win32 API exposes.

* [w32handle] Remove unrefing of handles on shutdown

If one of the handle is a file handle for example, then w32file has already be cleaned up, so we cannot guarantee that the handle we are going to close is not going to call into w32file code.