Add name of the Bourreau to the BackgroundActivityWorker process's command line

[prioux]

On a system where multiple BackgroundActivityWorker processes are started, by different configurations, it's difficult to recognize which worker belongs to which Bourreau configuration.

The main Bourreau process and and Task Worker processes all name themselves on their command line, but the BAC workers don't:

> ps xww -o "pid,lstart,time,args" 
    PID                  STARTED     TIME COMMAND
 811681 Thu Jun 12 10:39:43 2025 00:02:11 CBRAIN Server Bourreau AceLab-VH-2
 815107 Thu Jun 12 10:40:29 2025 01:20:24 BourreauActivity
 815438 Thu Jun 12 10:40:36 2025 00:01:57 /bin/bash script/watcher
 816056 Thu Jun 12 10:40:47 2025 00:01:07 BourreauWorker AceLab-VH-2

The same could be said of the watcher process too.

[prioux]

We could consider renaming them too: "TaskWorker", "TaskSubworker" and "ActivityWorker".