Add support for '30 suspends + 1 reboot' cycle

Add the following jobs:

- power-management/suspend-30-cycles-log-check-with-reboots
- power-management/suspend-30-cycle-log-attach-with-reboots
- power-management/suspend-30-cycles-time-check-with-reboots

Modifies the `pm_test` script to include `sleep_test` output in its logs in
order to easily access the data needed by `sleep_time_check` to compute
average times.

`sleep_time_check` has been updated to take into account more than one
sleep/resume times (the mean value is computed and returned).