Reboot - Windows provider should check new 'reboot_required' member for pending reboot status

As part of handling DSC's Invoke-DscResource returning a RebootRequired value, and not setting a global state, it is now necessary to set a status on the reboot resources provider.

Per MODULES-2641, we have decided on using the member `reboot_required`.

While this doesn't strictly block MODULES-2641 (based on the code for that ticket being defensive), this fix is necessary to handle DSC reboot requests. A new release of the reboot module will be required with these fixes.