Windows package provider should set working directory (cwd)

Some installations may require files other than the installer to install properly. The assumption of these installation packages may be that the path to these files is the current working directory.

However, the Windows package provider currently does not set a working directory - and hence cannot currently support certain types of installations.

PUP-6919 tracks the work to support cwd with the underlying Puppet::Util::Execution.execute mechanism. This ticket is to track setting the cwd automatically to the same location as the installer source.