This code path is used when frames are rendered as textures through
GstVideoGLTextureUploadMeta with EGL, mainly under Wayland.
Originally the EGLImage was exported as GEM, which was handled by
Intel drivers, but Gallium ones cannot create VA surfaces from
GEM buffers, only DMABuf.
This patch checks the memory types supported by VA driver to choose
the render the EGLImages from GEM or DMABuf, because GEM is still
better where supported.
DMABuf is well handled either by intel-vaapi-driver and gallium.
Fixes: #137
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer-vaapi/-/merge_requests/122>
Add initial support for EGL to libgstvaapi core library. The target
display server and the desired OpenGL API can be programmatically
selected at run-time.
A comprehensive set of EGL utilities are provided to support those
dynamic selection needs, but also most importantly to ensure that
the GL command stream is executed from within a single thread.
https://bugzilla.gnome.org/show_bug.cgi?id=743846
