Record and check process start time

[Hopding]

This PR causes the start time of each spawned process to be recorded in the processes.json file. This allows chip to detect when a new process is using the same PID as a process it had formerly spawned.

One scenario that can cause this to happen is rebooting your machine while chip processes are running. When your machine reboots, those chip processes are all gone. But your machine might use some PIDs that chip has stored in processes.json for system startup processes. Chip will then see these processes (e.g. with chip list) and think it created them because they have the same PID.

Recording and comparing the start time of processes in addition to their PID resolves this. In the example above, the start time of the new system processes would differ because they would have started after the reboot, but the chip.yml would have recorded start times from before the reboot.