Use the same file `os_handle.h` on both
Linux and Windows.
Change implementation of `HandleType` -> `UnifiedHandle` to
`std::variant<int, void *>`
use `int` on Linux
use `void *` on Windows
Related-To: NEO-8092
Signed-off-by: Fabian Zwolinski <fabian.zwolinski@intel.com>
Fabian Zwolinski