This tries to avoid "scrambled" image on Linux with Intel GPUs that are mostly used
together with x86 CPUs at the expense of using slightly slower non-direct DMABuf import,
by not going with GLES by default on EGL.
The "GST_GL_API" env can still be used to force one or another context type.
We need for GStreamer to be aware of currently used DRM modifier first. On the other
hand forcing GL everywhere would break most embedded systems that only work with GLES,
so do it for x86 processors only... and pray for it to work.
See: https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/1236
Make GL base importer class and all its subclasses that access parent props,
use a different mutex lock then the main importer class.
This way main importer class can continue processing buffers without waiting for
GL-based subclasses, as most GL operations (e.g. upload) are time consuming.
