Seen in an exception stack trace: we are wrapping `ApiFilteringActionFilter` around itself many times, once per filtered action, so effectively every action is doing a linear scan of the filtered actions, implemented recursively. I'm pretty sure a hashmap would be more efficient, and would avoid inflating the stack so much too.

```
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:86) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.action.support.ActionFilter$Simple.apply(ActionFilter.java:53) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:84) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.xpack.core.api.filtering.ApiFilteringActionFilter.apply(ApiFilteringActionFilter.java:53) ~[?:?]
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:84) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.xpack.core.api.filtering.ApiFilteringActionFilter.apply(ApiFilteringActionFilter.java:53) ~[?:?]
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:84) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.xpack.core.api.filtering.ApiFilteringActionFilter.apply(ApiFilteringActionFilter.java:53) ~[?:?]
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:84) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.xpack.core.api.filtering.ApiFilteringActionFilter.apply(ApiFilteringActionFilter.java:53) ~[?:?]
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:84) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.xpack.core.api.filtering.ApiFilteringActionFilter.apply(ApiFilteringActionFilter.java:53) ~[?:?]
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:84) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.xpack.core.api.filtering.ApiFilteringActionFilter.apply(ApiFilteringActionFilter.java:53) ~[?:?]
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:84) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.xpack.core.api.filtering.ApiFilteringActionFilter.apply(ApiFilteringActionFilter.java:53) ~[?:?]
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:84) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.xpack.core.api.filtering.ApiFilteringActionFilter.apply(ApiFilteringActionFilter.java:53) ~[?:?]
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:84) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.xpack.core.api.filtering.ApiFilteringActionFilter.apply(ApiFilteringActionFilter.java:53) ~[?:?]
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:84) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.xpack.core.api.filtering.ApiFilteringActionFilter.apply(ApiFilteringActionFilter.java:53) ~[?:?]
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:84) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.xpack.core.api.filtering.ApiFilteringActionFilter.apply(ApiFilteringActionFilter.java:53) ~[?:?]
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:84) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.xpack.core.api.filtering.ApiFilteringActionFilter.apply(ApiFilteringActionFilter.java:53) ~[?:?]
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:84) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at co.elastic.elasticsearch.api.validation.PublicSettingsValidationActionFilter.apply(PublicSettingsValidationActionFilter.java:101) ~[?:?]
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:84) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.xpack.core.api.filtering.ApiFilteringActionFilter.apply(ApiFilteringActionFilter.java:53) ~[?:?]
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:84) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.xpack.core.api.filtering.ApiFilteringActionFilter.apply(ApiFilteringActionFilter.java:53) ~[?:?]
    at org.elasticsearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:84) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
    at org.elasticsearch.xpack.security.action.filter.SecurityActionFilter.lambda$applyInternal$3(SecurityActionFilter.java:163) ~[?:?]
    at org.elasticsearch.action.ActionListenerImplementations$DelegatingFailureActionListener.onResponse(ActionListenerImplementations.java:212) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
```
server/src/main/java/org/elasticsearch/action/ActionModule.java
actions.register(FetchHealthInfoCacheAction.INSTANCE, FetchHealthInfoCacheAction.TransportAction.class);
        
        actions.register(PutSynonymsAction.INSTANCE, TransportPutSynonymsAction.class);
        actions.register(GetSynonymsAction.INSTANCE, TransportGetSynonymsAction.class);
        actions.register(DeleteSynonymsAction.INSTANCE, TransportDeleteSynonymsAction.class);
        actions.register(GetSynonymsSetsAction.INSTANCE, TransportGetSynonymsSetsAction.class);
        actions.register(PutSynonymRuleAction.INSTANCE, TransportPutSynonymRuleAction.class);
        actions.register(GetSynonymRuleAction.INSTANCE, TransportGetSynonymRuleAction.class);
        actions.register(DeleteSynonymRuleAction.INSTANCE, TransportDeleteSynonymRuleAction.class);
        return unmodifiableMap(actions.getRegistry());
    }
    private static ActionFilters setupActionFilters(List<ActionPlugin> actionPlugins) {
        return new ActionFilters(
            Collections.unmodifiableSet(actionPlugins.stream().flatMap(p -> p.getActionFilters().stream()).collect(Collectors.toSet()))
        );
    }
    public void initRestHandlers(Supplier<DiscoveryNodes> nodesInCluster) {
        List<AbstractCatAction> catActions = new ArrayList<>();
        Predicate<AbstractCatAction> catActionsFilter = restExtension.getCatActionsFilter();
        Predicate<RestHandler> restFilter = restExtension.getActionsFilter();
        Consumer<RestHandler> registerHandler = handler -> {
            if (restFilter.test(handler)) {
                if (handler instanceof AbstractCatAction catAction && catActionsFilter.test(catAction)) {
                    catActions.add(catAction);
                }
                restController.registerHandler(handler);
            } else {
                /*
                 * There's no way this handler can be reached, so we just register a placeholder so that requests for it are routed to
                 * RestController for proper error messages.