Add "Enable Mouse-based Gyro" setting to I/O config (#18835)

This is a continuation of my work on #18113.

Addresses issue #18197.

Adds a new checkbox in the I/O settings tab that enables mouse-based
gyro emulation at game startup, making the feature more discoverable to
users.

rpcs3/Input/mouse_gyro_handler.cpp

@@ -26,6 +26,12 @@ bool mouse_gyro_handler::toggle_enabled()
 	return m_enabled;
 }
 
+void mouse_gyro_handler::set_enabled(bool enabled)
+{
+	m_enabled = enabled;
+	clear();
+}
+
 void mouse_gyro_handler::set_gyro_active()
 {
 	gui_log.notice("Mouse-based gyro activated");

rpcs3/Input/mouse_gyro_handler.h

@@ -13,6 +13,7 @@ class mouse_gyro_handler
 public:
 	void clear();
 	bool toggle_enabled();
+	void set_enabled(bool enabled);
 
 	void handle_event(QEvent* ev, const QWindow& win);
 	void apply_gyro(const std::shared_ptr<Pad>& pad);

rpcs3/Input/pad_thread.cpp

@@ -82,7 +82,7 @@ void pad_thread::Init()
 	std::lock_guard lock(pad::g_pad_mutex);
 
 	// Reset mouse-based gyro state
-	m_mouse_gyro.clear();
+	m_mouse_gyro.set_enabled(g_cfg.io.mouse_based_gyro_enabled.get());
 
 	// Cache old settings if possible
 	std::array<pad_setting, CELL_PAD_MAX_PORT_NUM> pad_settings;