[core, hle, video_core, memory] Improve multi-process, display layers, dynamic shader cache and rework overlay (#4238)

- [x] I have read and followed the [Contribution Guidelines](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/CONTRIBUTING.md#code-contributions).
- [x] I have read and followed the [AI Policy](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/docs/policies/AI.md)
- [x] I have read and followed the [Coding Guidelines](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/docs/policies/Coding.md) to the best of my ability.

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

- Dynamic shader cache reloading capability for qlaunch
- Multi-process improvements (thanks to @frank1734), instead of just using the main application we now respect caller process (also did it for HID devices while I was at it)
- Layer stack masks & shared buffer screenshot for video core, added different masks (screenshot, recording, etc.) this was discovered as an issue due to how in qlaunch the transition was not right between applications. May not be perfect but also fixes screenshots while using qlaunch
- Reworked overlay display management (input and visibility) - instead of random numbers as I've previously did, I decided to add an AppletZIndex enum for better readability. Also split capability of input by touch and gamepad.
- etc.

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4238
Reviewed-by: Samuel <lizzie@eden-emu.dev>
Reviewed-by: CamilleLaVey <camillelavey99@gmail.com>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

src/core/core.cpp

@@ -295,6 +295,10 @@ struct System::Impl {
     SystemResultStatus Load(System& system, Frontend::EmuWindow& emu_window, const std::string& filepath, Service::AM::FrontendAppletParameters& params) {
         InitializeKernel(system);
 
+        if (params.applet_type == Service::AM::AppletType::Application) {
+            current_application_filepath = filepath;
+        }
+
         const auto file = GetGameFileFromPath(virtual_filesystem, filepath);
 
         // Create the application process
@@ -330,7 +334,7 @@ struct System::Impl {
         LaunchTimestampCache::SaveLaunchTimestamp(params.program_id);
 
         // Make the process created be the application
-        kernel.MakeApplicationProcess(process->GetHandle());
+        kernel.SetApplicationProcess(process->GetHandle());
 
         // Set up the rest of the system.
         SystemResultStatus init_result{SetupForApplicationProcess(system, emu_window)};
@@ -467,6 +471,7 @@ struct System::Impl {
     Core::SpeedLimiter speed_limiter;
     ExecuteProgramCallback execute_program_callback;
     ExitCallback exit_callback;
+    ApplicationChangedCallback application_changed_callback;
 
     std::optional<Service::Services> services;
     std::optional<Core::Debugger> debugger;
@@ -488,6 +493,8 @@ struct System::Impl {
     std::array<u64, Core::Hardware::NUM_CPU_CORES> dynarmic_ticks{};
     std::array<u8, 0x20> build_id{};
 
+    std::string current_application_filepath;
+
     /// Service manager
     std::shared_ptr<Service::SM::ServiceManager> service_manager;
     /// ContentProviderUnion instance
@@ -727,7 +734,25 @@ const Core::SpeedLimiter& System::SpeedLimiter() const {
 }
 
 u64 System::GetApplicationProcessProgramID() const {
-    return impl->kernel.ApplicationProcess()->GetProgramId();
+    const auto* const process = impl->kernel.ApplicationProcess();
+    return process != nullptr ? process->GetProgramId() : 0;
+}
+
+u64 System::GetProgramIdForProcessId(u64 process_id) const {
+    auto process = impl->kernel.GetProcessByProcessId(process_id);
+    return process.IsNull() ? 0 : process->GetProgramId();
+}
+
+u64 System::ResolveCallerProgramId(u64 process_id) const {
+    if (const auto program_id = this->GetProgramIdForProcessId(process_id); program_id != 0) {
+        return program_id;
+    }
+
+    const auto fallback = this->GetApplicationProcessProgramID();
+    LOG_WARNING(Core,
+                "Could not resolve caller process_id={}, falling back to application {:016X}",
+                process_id, fallback);
+    return fallback;
 }
 
 Loader::ResultStatus System::GetGameName(std::string& out) const {
@@ -910,6 +935,10 @@ void System::ExecuteProgram(std::size_t program_index) {
     }
 }
 
+const std::string& System::GetCurrentApplicationFilePath() const {
+    return impl->current_application_filepath;
+}
+
 /// @brief Gets a reference to the user channel stack.
 /// It is used to transfer data between programs.
 std::vector<std::vector<u8>>& System::GetUserChannel() {
@@ -961,6 +990,18 @@ void System::Exit() {
     }
 }
 
+void System::RegisterApplicationChangedCallback(ApplicationChangedCallback&& callback) {
+    impl->application_changed_callback = std::move(callback);
+}
+
+void System::NotifyApplicationChanged(u64 program_id) {
+    //LOG_DEBUG(Core, "Running application changed to {:016X}", program_id);
+
+    if (impl->application_changed_callback) {
+        impl->application_changed_callback(program_id);
+    }
+}
+
 void System::ApplySettings() {
     impl->RefreshTime(*this);