(PUP-839) FFI Windows::Util::Security.set_privilege

• Don't call LookupPrivilegeValue directly anymore, instead call Puppet::Util::Windows::Process.lookup_privilege_value which has already been FFI'd. Use FFI structs for LUID_AND_ATTRIBUTES and TOKEN_PRIVILEGES
• Ensure that set_privilege has a well-defined return value of true when it succeeds, or raises otherwise.
• Remove TOKEN_QUERY privilege since AdjustTokenPrivileges is not filling in a buffer with existing LUID information.