Draft: vlc_gyroscope: add new API for viewpoint providers, add android_sensors and win32_sensors

The API is a bit simplistic for now, but it allows refactoring the gyroscopic code out of the display plugins, in particular to remove the specific glwin32.c code for Windows (!1387).

It's inspired from original Adrien's viewpoint provider work.

Co-authored-by: Adrien Maglo magsoft@videolan.org

This adds support for this new capability on Win32 sensors (which is the main point of the MR) and Android sensors (new feature, which I needed to actually test the code and ensure the quaternion part works in addition to the tests).

Currently marked as draft since I still need to finish win32_sensors part, and I'd like to merge the mouse + add a libvlc API (or disable by default at least) + document a bit more, and a few commits need to be cleaned up in the android_sensors module.

Please check the API itself. I prepared a notification API (event callback) but it does not necessarily make sense to forward to set_viewpoint immediately so there is no consumer for it yet. :)

I haven't tested the audio part.