Fix persistent GL_INVALID_OPERATION spam and resolution-change bugs on Android

- opengl_end_frame() bound framebuffer 0 on Android, which has no valid
  target there (real presentation goes through the OpenXR swapchain's own
  FBOs) - gl4es reported this every frame. Skip it there.
- render_hack_cameras() re-entered opengl_start_frame()/opengl_end_frame()
  for camera-monitor renders that never touch the GL screen; excluded them
  to match use_opengl()'s existing behavior. Also drains a stray error left
  by xrPollEvent().
- ChangeScreenSize() never called opengl_resize() on Android, freezing the
  3D render target at launch size after an in-game resolution change; and
  xr_get_game_resolution() used the swapchain's fixed size instead of the
  current screen resolution, misplacing the laser-pointer cursor after such
  a change.
- Removes all temporary bisection diagnostics added while tracking down the
  GL_INVALID_OPERATION source.

android/app/src/main/cpp/xr_swapchain.c

@@ -149,6 +149,7 @@ bool xr_swapchain_acquire(XrInstance instance, XrSwapchainState *state) {
     // (android_draw_surface_as_quad()) land in the right place.
     glBindFramebuffer(GL_FRAMEBUFFER, state->fbos[imageIndex]);
     glViewport(0, 0, state->width, state->height);
+
     return true;
 }