gdkglcontext.c: Ensure EGL contexts are in-sync with shared context

gdkglcontext.c: Ensure EGL contexts are in-sync with shared context

The EGL context that we are actually creating must have matching OpenGL/ES
versions and allowed GL API set with the previously-created EGL context
that will be shared with it so that they can interoperate together, if
applicable.

This will fix the situation by making sure that we request for the
OpenGL/ES version and OpenGL API set that match with what we have in our shared
EGL context.  Otherwise, the newly-created EGL context assumed a OpenGL/ES 2.0
context that supported desktop OpenGL, which may not be what we wanted, such as
in the case of libANGLE.