[COOK-3826] Allow `chef-client::task` to use cron schedule

Added `cron_to_task_schedule` helper method to convert cron minute and hour schedules into something windows task scheduler can use.
Added rspec tests for `cron_to_task_schedule` to test the complicated logic for various cron schedules

Also these fixes:
Changed the task to run as SYSTEM because it doesn't make sense to me to run chef-client in the foreground with a scheduled task, kind of defeats the purpose IMHO.
Change the command being run by the scheduled task so `STDOUT.tty?` will be false. This is so the logging will work correctly (similar to how the same thing is done with `chef-client::cron`)