Propagate CoordinatedShutdown reason to application exit code

[Arkatufus]

Fixes #7517
Superseeds #7680

Changes

• If "exit-clr" HOCON options is set and the CoordinatedShutdown stack was run, its reason will be propagated to the Environment.Exit() call.
• Exit codes conforms to the Linux exit code convention

See: https://manpages.ubuntu.com/manpages/lunar/man3/sysexits.h.3head.html
See: https://manpages.ubuntu.com/manpages/noble/man3/EXIT_SUCCESS.3const.html

Possible Exit Codes

Exit code	Description
0	ActorSystem shutdown cleanly due to .Terminate(), .Abort(), or normal cluster events
1	Unknown shutdown cause
3	[CLUSTER] ActorSystem terminated because it is downed
4	[CLUSTER] ActorSystem terminated because it failed to join the cluster

[Aaronontheweb]

LGTM