EGLWindow: Clean up some init attribute code.
EGLWindow: Clean up some init attribute code.

EGL_CONTEXT_OPENGL_DEBUG is only exposed as of EGL 1.5.
We can also now properly test for no_error extension strings.
Do not require backwards compatible context extensions.

Fixes parts of using EGLWindow to load native EGL drivers.

Bug: angleproject:4596
Change-Id: I4de8f492f265d29f6603ed1b35b123e362699c54
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2176271
Commit-Queue: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>
Reviewed-by: Yuly Novikov <36f5580f63d0a3eacc17e89a61d11e2f646630d2@chromium.org>

ppy/angle,ppy/angle,ppy/angle,ppy/angle