Reintroduce event groups

This started with reverting commit 52cd02173d
and then rewriting it to be per handler rather than handler identifier
and adding support for hooks as well as adding implicit module groups.

src/EventRegistry.cc

@@ -146,4 +146,69 @@ void EventRegistry::ActivateAllHandlers()
 		}
 	}
 
+EventGroupPtr EventRegistry::RegisterGroup(EventGroupKind kind, std::string_view name)
+	{
+	auto key = std::pair{kind, std::string{name}};
+	if ( const auto& it = event_groups.find(key); it != event_groups.end() )
+		return it->second;
+
+	auto group = std::make_shared<EventGroup>(kind, name);
+	return event_groups.emplace(key, group).first->second;
+	}
+
+EventGroupPtr EventRegistry::LookupGroup(EventGroupKind kind, std::string_view name)
+	{
+	auto key = std::pair{kind, std::string{name}};
+	if ( const auto& it = event_groups.find(key); it != event_groups.end() )
+		return it->second;
+
+	return nullptr;
+	}
+
+EventGroup::EventGroup(EventGroupKind kind, std::string_view name) : kind(kind), name(name) { }
+
+EventGroup::~EventGroup() noexcept { }
+
+// Run through all ScriptFunc instances associated with this group and
+// update their bodies after a group's enable/disable state has changed.
+//
+// EventGroup is private friend with Func, so fiddeling with the bodies
+// directly works and keeps the logic away from Func for now.
+void EventGroup::UpdateFuncBodies()
+	{
+	static auto is_disabled = [](const auto& g)
+	{
+		return g->IsDisabled();
+	};
+
+	for ( const auto& func : funcs )
+		for ( auto& b : func->bodies )
+			b.disabled = std::any_of(b.groups.cbegin(), b.groups.cend(), is_disabled);
+	}
+
+void EventGroup::Enable()
+	{
+	if ( enabled )
+		return;
+
+	enabled = true;
+
+	UpdateFuncBodies();
+	}
+
+void EventGroup::Disable()
+	{
+	if ( ! enabled )
+		return;
+
+	enabled = false;
+
+	UpdateFuncBodies();
+	}
+
+void EventGroup::AddFunc(detail::ScriptFuncPtr f)
+	{
+	funcs.insert(f);
+	}
+
 	} // namespace zeek