Add break for default cases

Visual Studio has an option to search all files in a solution, so I
did a search in there for "default:" looking for any missing break
statements.

I've left out default statements that return something, and that throw
something, even if via ThrowInvalidType. UNREACHABLE leads towards throw

R_THROW macro leads towards a return

src/yuzu/main.cpp

@@ -1953,6 +1953,7 @@ void GMainWindow::OnGameListOpenFolder(u64 program_id, GameListOpenTarget target
     }
     default:
         UNIMPLEMENTED();
+        break;
     }
 
     const QString qpath = QString::fromStdString(Common::FS::PathToUTF8String(path));
@@ -3182,6 +3183,7 @@ void GMainWindow::OnToggleGpuAccuracy() {
     case Settings::GPUAccuracy::Extreme:
     default: {
         Settings::values.gpu_accuracy.SetValue(Settings::GPUAccuracy::High);
+        break;
     }
     }
 
@@ -3514,6 +3516,7 @@ void GMainWindow::UpdateGPUAccuracyButton() {
     default: {
         gpu_accuracy_button->setText(tr("GPU ERROR"));
         gpu_accuracy_button->setChecked(true);
+        break;
     }
     }
 }