refactor(rule_engine): test 'ok' results in one dedicated function

apps/emqx_rule_engine/src/emqx_rule_runtime.erl

@@ -508,8 +508,6 @@ nested_put(Alias, Val, Columns0) ->
     emqx_rule_maps:nested_put(Alias, Val, Columns).
 
 -define(IS_RES_DOWN(R), R == stopped; R == not_connected; R == not_found).
-inc_action_metrics(ok, RuleId) ->
-    emqx_metrics_worker:inc(rule_metrics, RuleId, 'actions.success');
 inc_action_metrics({error, {recoverable_error, _}}, RuleId) ->
     emqx_metrics_worker:inc(rule_metrics, RuleId, 'actions.failed.out_of_service');
 inc_action_metrics(?RESOURCE_ERROR_M(R, _), RuleId) when ?IS_RES_DOWN(R) ->
@@ -525,6 +523,8 @@ inc_action_metrics(R, RuleId) ->
             emqx_metrics_worker:inc(rule_metrics, RuleId, 'actions.success')
     end.
 
+is_ok_result(ok) ->
+    true;
 is_ok_result(R) when is_tuple(R) ->
     ok == erlang:element(1, R);
 is_ok_result(_) ->