gio/win32: add GMemoryMonitorWin32

Windows has CreateMemoryResourceNotification() API:

https://docs.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-creatememoryresourcenotification

It only notifies whether "Available physical memory is running low."

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

gio/meson.build

@@ -423,6 +423,7 @@ else
   platform_deps += uwp_gio_deps
 
   win32_sources += files(
+    'gmemorymonitorwin32.c',
     'gwin32registrykey.c',
     'gwin32mount.c',
     'gwin32volumemonitor.c',