[applet] add post exit cleanups to frontend applets to avoid accumulation (#4457)

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-------------------

Maran reported MK8D if one press Plus button 38 times.
This could be impacting other games around, but 4442 already quenched the spontaneous accumulation cases, by avoiding multiple event signals. MK8D is an atypical induced example.
The reason was a controller applet accumulation, as we had no proper way to keep track and erase child applets on exit.
Now we have. Enjoy your Plus button rushing fetish!

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4457
Reviewed-by: lizzie <lizzie@eden-emu.dev>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

src/core/hle/service/am/frontend/applets.cpp

@@ -29,6 +29,7 @@
 #include "core/hle/service/am/frontend/applet_web_browser.h"
 #include "core/hle/service/am/frontend/applets.h"
 #include "core/hle/service/am/service/storage.h"
+#include "core/hle/service/am/window_system.h"
 #include "core/hle/service/sm/sm.h"
 
 namespace Service::AM::Frontend {
@@ -72,10 +73,16 @@ void FrontendApplet::PushInteractiveOutData(std::shared_ptr<IStorage> storage) {
 
 void FrontendApplet::Exit() {
     auto applet_ = applet.lock();
-
-    std::scoped_lock lk{applet_->lock};
-    applet_->is_completed = true;
-    applet_->state_changed_event.Signal(system.Kernel());
+    {
+        std::scoped_lock lk{applet_->lock};
+        applet_->is_completed = true;
+        applet_->state_changed_event.Signal(system.Kernel());
+    }
+    if (auto caller_applet = applet_->caller_applet.lock()) {
+        std::scoped_lock lk{caller_applet->lock};
+        std::erase(caller_applet->child_applets, applet_);
+    }
+    if (auto* window_system = system.GetAppletManager().GetWindowSystem()) window_system->RequestUpdate();
 }
 
 FrontendAppletSet::FrontendAppletSet() = default;

src/core/hle/service/am/service/library_applet_creator.cpp

@@ -122,7 +122,10 @@ std::shared_ptr<ILibraryAppletAccessor> CreateGuestApplet(Core::System& system,
         auto broker = std::make_shared<AppletDataBroker>(system);
         applet->caller_applet = caller_applet;
         applet->caller_applet_broker = broker;
-        caller_applet->child_applets.push_back(applet);
+        {
+            std::scoped_lock lk{caller_applet->lock};
+            caller_applet->child_applets.push_back(applet);
+        }
         window_system.TrackApplet(applet, false);
         return std::make_shared<ILibraryAppletAccessor>(system, broker, applet);
     }
@@ -148,10 +151,10 @@ std::shared_ptr<ILibraryAppletAccessor> CreateFrontendApplet(Core::System& syste
     applet->caller_applet = caller_applet;
     applet->caller_applet_broker = storage;
     applet->frontend = system.GetFrontendAppletHolder().GetApplet(applet, applet_id, mode);
-    caller_applet->child_applets.push_back(applet);
-
-    window_system.TrackApplet(applet, false);
-
+    {
+        std::scoped_lock lk{caller_applet->lock};
+        caller_applet->child_applets.push_back(applet);
+    }
     return std::make_shared<ILibraryAppletAccessor>(system, storage, applet);
 }