(PUP-2521) Define Process constants locally

 - Previously, Process constants were used in a few locations throughout
   the code.  Capture the needed PRIORITY_CLASS constants in our local
   Windows Process class, and also define CREATE_NEW_CONSOLE.  These
   constants have moved in new versions of the win32-process gem.
 - Note that ext/windows/service/daemon.rb doesn't load Puppet code.
   The daemon only loads what it explicitly needs, so ensure the
   CREATE_NEW_CONSOLE constant is defined there.
(PUP-2521) Remove windows-pr mixins from daemon

 - synchronize and handle appear to no longer be used