mesa: fold GL ES 3 packages into GL ES 2 ones

mesa: fold GL ES 3 packages into GL ES 2 ones

OpenGL ES 3 is closely tied to the OpenGL ES 2: there is no separate
library, one can use GL ES 2 headers for GL ES 3 app, etc. Instead of
having separate packages, merge GL ES 3 packages into GL ES 2 ones.

Suggested-by: Böszörményi Zoltán <zboszor@gmail.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>