[call-v3] Correctly detect v3 filters even if the immediate base class is not ImplementCallFilter<> (#35997)

Fixes max_age filter not getting a v3 init_call implementation

Closes #35997

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/35997 from ctiller:naughty df17e57e91
PiperOrigin-RevId: 610194630

src/core/ext/filters/channel_idle/channel_idle_filter.cc

@@ -294,6 +294,7 @@ const grpc_channel_filter MaxAgeFilter::kFilter =
     MakePromiseBasedFilter<MaxAgeFilter, FilterEndpoint::kServer>("max_age");
 
 void RegisterChannelIdleFilters(CoreConfiguration::Builder* builder) {
+  GPR_ASSERT(MaxAgeFilter::kFilter.init_call != nullptr);
   if (!IsV3ChannelIdleFiltersEnabled()) return;
   builder->channel_init()
       ->RegisterFilter<ClientIdleFilter>(GRPC_CLIENT_CHANNEL)

src/core/lib/channel/promise_based_filter.h

@@ -1065,8 +1065,10 @@ MakeFilterCall(Derived* derived) {
 //   the filter does not intercept call finalization.
 // - void OnFinalize(const grpc_call_final_info*):
 //   the filter intercepts call finalization.
+class ImplementChannelFilterTag {};
 template <typename Derived>
-class ImplementChannelFilter : public ChannelFilter {
+class ImplementChannelFilter : public ChannelFilter,
+                               public ImplementChannelFilterTag {
  public:
   // Natively construct a v3 call.
   void InitCall(CallSpineInterface* call_spine) {
@@ -1914,7 +1916,7 @@ struct ChannelFilterWithFlagsMethods {
 template <typename F, FilterEndpoint kEndpoint, uint8_t kFlags = 0>
 absl::enable_if_t<
     std::is_base_of<ChannelFilter, F>::value &&
-        !std::is_base_of<ImplementChannelFilter<F>, F>::value &&
+        !std::is_base_of<ImplementChannelFilterTag, F>::value &&
         !std::is_base_of<HackyHackyHackySkipInV3FilterStacks, F>::value,
     grpc_channel_filter>
 MakePromiseBasedFilter(const char* name) {
@@ -2001,7 +2003,7 @@ MakePromiseBasedFilter(const char* name) {
 }
 
 template <typename F, FilterEndpoint kEndpoint, uint8_t kFlags = 0>
-absl::enable_if_t<std::is_base_of<ImplementChannelFilter<F>, F>::value,
+absl::enable_if_t<std::is_base_of<ImplementChannelFilterTag, F>::value,
                   grpc_channel_filter>
 MakePromiseBasedFilter(const char* name) {
   using CallData = promise_filter_detail::CallData<kEndpoint>;