MEDIUM: mworker: display a more accessible message when a worker crash

MEDIUM: mworker: display a more accessible message when a worker crash

Should fix issue #1034.

Display a more accessible message when a worker crash about what to do.

Example:

	$ ./haproxy -W -f haproxy.cfg
	[NOTICE]   (308877) : New worker (308884) forked
	[NOTICE]   (308877) : Loading success.
	[NOTICE]   (308877) : haproxy version is 2.9-dev4-d90d3b-58
	[NOTICE]   (308877) : path to executable is ./haproxy
	[ALERT]    (308877) : Current worker (308884) exited with code 139 (Segmentation fault)
	[WARNING]  (308877) : A worker process unexpectedly died and this can only be explained by a bug in haproxy or its dependencies.
	Please check that you are running an up to date and maintained version of haproxy and open a bug report.
	HAProxy version 2.9-dev4-d90d3b-58 2023/09/05 - https://haproxy.org/
	Status: development branch - not safe for use in production.
	Known bugs: https://github.com/haproxy/haproxy/issues?q=is:issue+is:open
	Running on: Linux 6.2.0-31-generic #31-Ubuntu SMP PREEMPT_DYNAMIC Mon Aug 14 13:42:26 UTC 2023 x86_64
	[ALERT]    (308877) : exit-on-failure: killing every processes with SIGTERM
	[WARNING]  (308877) : All workers exited. Exiting... (139)