[GStreamer] port video sink to gst-gl

In GStreamer 1.4 gst-egl features were merged in gst-gl.
The player's ::updateTexture() method now first check the buffer
memory before attempting to access the GLTextureUploadMeta because the
EGL allocator unconditionally binds the latter to the buffers it
creates. We want to prefer using EGLImages instead of the
TextureUploadMeta.