Expand monitor_process to handle multiple processes

[BrianJKoopman]

_internal.monitor_process currently monitors the ACU agent's generate_scan process during a scan, and will raise if the process crashes. However there are more processes we need to monitor during scans. monitor_process should be expanded to take in a list of processes to monitor. This will include the smurf stream processes, for example.

[BrianJKoopman]

There was a recent crash on satp1 (run 1658) where all pysmurf-controller agents crashed due to a networking issue, but the ACU continued to scan until the end of the scan (~45 minutes.) The schedule crashed on the next pysmurf command, but it would have been better if we were actively monitoring the streaming processes and crashed out earlier.