(PUP-838) FFI Puppet::Util::Windows::Process module

~~Builds on PUP-836 #2675 which needs to be merged first.~~
~~Builds on PUP-2554 #2677 which needs to be merged first.~~

- Moved FFI code to the bottom of the class in 4422846
- Remove  dependency on windows/process, windows/handle, and
   windows/synchronize, all part of windows-pr (which is not a gem that is
   currently FFI-ed, even in the latest release)
- Add WAIT_TIMEOUT from Windows::Synchronize
- FFI WaitForSingleObject
- FFI GetExitCodeProcess