Draft: implement resizing through vout_window_t module on iOS

This merge request implements the resizing through the vout_window_t module, removing the need for the OpenGL module to fail on MakeCurrent.

To really make this possible, the rendering is also stopped when the application is put into the background, where no rendering is allowed or wanted anyway.

Resend from https://patches.videolan.org/patch/31498/, including the change on the report function to use booleans, and the change on the lock to use display lock.

Thanks to @umxprime for the multiple investigation and fixes in this patchset!

Draft because I probably need to split the last commit, and integrate more fixes from @umxprime for constraints.