fusee/exo: add ability to disable user exception handlers

please do not use this
yellows8 needs it to debug am, 99% of use cases want them on

exosphere/src/package2.c

@@ -538,6 +538,9 @@ void load_package2(coldboot_crt0_reloc_list_t *reloc_list) {
     /* Load Exosphere-specific config. */
     exosphere_load_config();
     configitem_set_debugmode_override(exosphere_should_override_debugmode_user() != 0, exosphere_should_override_debugmode_priv() != 0);
+    if (exosphere_should_disable_usermode_exception_handlers() != 0) {
+        configitem_disable_usermode_exception_handlers();
+    }
 
     /* Setup the Security Engine. */
     setup_se();