Extract libvlc jni binding from vlc-android code

This MR aims to move the libvlc JNI binding code to a dedicated repository https://code.videolan.org/videolan/libvlcjni

The main goal of this move is to be able to maintain parallel bindings version that target both libvlc v3 and v4.

I've kept the changes of the MR as minimal as possible. The commit history for libvlc/ has been preserved in https://code.videolan.org/videolan/libvlcjni. I've tested that most jobs are green https://code.videolan.org/mfkl/vlc-android/-/pipelines/219671.