Make Watchdog Signal Configurable

Allows configuring the watchdog signal (with a default of SIGABRT).
This allows an alternative to SIGABRT when coredumps are not desirable.

Appropriate references to SIGABRT or aborting were renamed to reflect
more liberal watchdog signals.

Closes #8658

src/basic/unit-def.c

@@ -169,7 +169,7 @@ static const char* const service_state_table[_SERVICE_STATE_MAX] = {
         [SERVICE_EXITED] = "exited",
         [SERVICE_RELOAD] = "reload",
         [SERVICE_STOP] = "stop",
-        [SERVICE_STOP_SIGABRT] = "stop-sigabrt",
+        [SERVICE_STOP_WATCHDOG] = "stop-watchdog",
         [SERVICE_STOP_SIGTERM] = "stop-sigterm",
         [SERVICE_STOP_SIGKILL] = "stop-sigkill",
         [SERVICE_STOP_POST] = "stop-post",

src/basic/unit-def.h

@@ -108,7 +108,7 @@ typedef enum ServiceState {
         SERVICE_EXITED,            /* Nothing is running anymore, but RemainAfterExit is true hence this is OK */
         SERVICE_RELOAD,
         SERVICE_STOP,              /* No STOP_PRE state, instead just register multiple STOP executables */
-        SERVICE_STOP_SIGABRT,      /* Watchdog timeout */
+        SERVICE_STOP_WATCHDOG,
         SERVICE_STOP_SIGTERM,
         SERVICE_STOP_SIGKILL,
         SERVICE_STOP_POST,