Fix kill => disable_all_heaters => print_job_timer.stop (#12146)

- Remove `print_job_timer.stop()` from `disable_all_heaters`
- Call `print_job_timer.stop()` for relevant `disable_all_heaters()`.
- Split up `kill()` for watchdog interrupt safety

Marlin/src/gcode/queue.cpp

@@ -391,7 +391,7 @@ inline void get_serial_commands() {
               wait_for_user = false;
             #endif
           }
-          if (strcmp(command, "M112") == 0) kill(PSTR(MSG_KILLED));
+          if (strcmp(command, "M112") == 0) kill();
           if (strcmp(command, "M410") == 0) quickstop_stepper();
         #endif