dsc_lite : Make Beaker tests consume dsc_puppetfakeresource

During the removal of vendored content / acceptance tests in https://github.com/puppetlabs/puppetlabs-dsc_lite/pull/3, 17 tests were left behind that continued to exercise the functionality of the powershell_manager / Invoke-DscResource integration through generated types. In particular, dsc_file, dsc_service and dsc_xservice were all left to satisfy the tests.

There is another custom resource called dsc_puppetfakeresource in the repository that is used for reboot tests. Since the dsc_lite repository will no longer vendor content, that type wrapper / DSC implementation can be repurposed to take the place of the dsc_file resource, removing the few files that remain in the repository as a result.