change how the userspace GLES drivers are named

for single library:
  /vendor/lib/egl/GLES.so

for multiple libraries:
  /vendor/lib/egl/EGL.so
  /vendor/lib/egl/GLESv1_CM.so
  /vendor/lib/egl/GLESv2.so

EGL_BOARD_CONFIG as well as egl.cfg are not needed anymore.

To facilitate the transition, the loader will also look
for the older naming scheme.

Bug: 8631636
Change-Id: Id4b113468df29bae72b323f76598229914e1c7a1