[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/qt_common/render/emu_thread.cpp

@@ -51,7 +51,18 @@ void EmuThread::run() {
             QtCommon::system->Run();
             m_stopped.Reset();
 
-            m_should_run_cv.wait(lk, stop_token, [&] { return !m_should_run; });
+            m_should_run_cv.wait(lk, stop_token, [&] {
+                return !m_should_run || m_pending_shader_cache_title.has_value();
+            });
+
+            if (m_should_run && m_pending_shader_cache_title.has_value()) {
+                const u64 program_id = *m_pending_shader_cache_title;
+                m_pending_shader_cache_title.reset();
+
+                lk.unlock();
+                this->ReloadDiskShaderCache(program_id);
+                lk.lock();
+            }
         } else {
             QtCommon::system->Pause();
             m_stopped.Set();
@@ -67,6 +78,32 @@ void EmuThread::run() {
     QtCommon::system->ShutdownMainProcess();
 }
 
+void EmuThread::ReloadDiskShaderCache(u64 program_id) {
+    if (!Settings::values.use_disk_shader_cache.GetValue()) {
+        return;
+    }
+
+    LOG_INFO(Frontend, "Reloading disk shader cache for {:016X}", program_id);
+
+    auto& system = *QtCommon::system;
+    auto& gpu = system.GPU();
+
+    system.Pause();
+    gpu.WaitForIdle();
+    gpu.ObtainContext();
+
+    emit ShaderCacheReloadStarted();
+    emit LoadProgress(VideoCore::LoadCallbackStage::Prepare, 0, 0);
+    system.Renderer().ReadRasterizer()->LoadDiskResources(program_id, m_stop_source.get_token(),
+        [this](VideoCore::LoadCallbackStage stage, std::size_t value, std::size_t total) {
+            emit LoadProgress(stage, value, total);
+        });
+    emit LoadProgress(VideoCore::LoadCallbackStage::Complete, 0, 0);
+    emit ShaderCacheReloadFinished();
+
+    gpu.ReleaseContext();
+}
+
 // Unlock while emitting signals so that the main thread can
 // continue pumping events.