py: Add mp_raise_type helper macro and use it where appropriate.

This provides a more consistent C-level API to raise exceptions, ie moving
away from nlr_raise towards mp_raise_XXX.  It also reduces code size by a
small amount on some ports.

ports/esp32/modmachine.c

@@ -196,7 +196,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_0(machine_reset_obj, machine_reset);
 
 STATIC mp_obj_t machine_soft_reset(void) {
     pyexec_system_exit = PYEXEC_FORCED_EXIT;
-    nlr_raise(mp_obj_new_exception(&mp_type_SystemExit));
+    mp_raise_type(&mp_type_SystemExit);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_0(machine_soft_reset_obj, machine_soft_reset);