Overhaul the VR menu UI: header, tabs, live video options, hover/click feedback, i18n, and dragging

- Header with title, git-tag-derived version, and a live FPS/frame-time/
  CPU/GPU-utilization/free-memory stats ribbon below the tab bar (FPS via
  a new per-frame tracker in xr_session.c; CPU/GPU via the OpenXR
  XR_META_performance_metrics extension, gracefully unavailable on
  runtimes that don't support it)
- Bottom tab bar with a live-editable Video Options tab (renderer/
  resolution), applying changes immediately via qs_config.c
- Hover and press feedback on every menu/keyboard button via a
  StateListDrawable (Android's default ripple never animates on this
  permanently unattached view tree), with a lighter default button color
  for visibility
- i18n for all menu/keyboard chrome text, following the game's own
  language setting (Strings.java)
- The main menu is now draggable via its header, matching the keyboard;
  xr_input.c's drag handling is generalized to per-overlay state instead
  of being keyboard-only
- The keyboard's title bar now matches the menu header's style

android/app/src/main/cpp/xr_session.h

@@ -83,6 +83,21 @@ void xr_get_game_quad_extent(float *distance_m, float *half_width_m, float *half
 // swapchain.
 void xr_get_game_resolution(int *width, int *height);
 
+// Exponentially-smoothed frame rate/frame time, updated once per real
+// rendered frame in xr_frame_end() - read by MenuOverlay's header (see
+// questshock_native.c's nativeGetFps()/nativeGetFrameTimeMs()). 0 before
+// the second frame has run (nothing to compute a delta from yet).
+float xr_session_get_fps(void);
+float xr_session_get_frame_ms(void);
+
+// Device-wide CPU/GPU utilization percentage (0-100), via the
+// XR_META_performance_metrics extension - same per-frame update cadence as
+// the FPS/frame-time getters above. Returns -1.0f if the extension isn't
+// supported by the runtime, or its cpu_utilization/gpu_utilization counter
+// couldn't be found among the ones it advertises.
+float xr_session_get_cpu_utilization(void);
+float xr_session_get_gpu_utilization(void);
+
 #ifdef __cplusplus
 }
 #endif