Revert "egl: put full path to libEGL_mesa.so in GLVND json"

Revert "egl: put full path to libEGL_mesa.so in GLVND json"

This reverts commit 0021f7dc307f4852955359adb5ac2b7667e6d4ac.

That commit had 2 issues:
- I missed the `.0` from the filename, causing issues on Debian & Ubuntu
  platforms.
- I didn't think about multilib/multi-arch systems, where we'd now need
  a separate json for each arch as they point to different libs.

Reverting this commit for now, I'll try again later.

Requested-by: Michel Dänzer <michel@daenzer.net>
Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/2466
Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/2471
Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/2480
Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3726>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3726>