The ASSERT macro is enabled with ANGLE_RELEASE_ASSERT, so we should
use the same behaviour as the normal ASSERT for the other debug
macros.

Also remove UNREACHABLEs in the format validation code that were
being hit silently.

Also make some EGL tests skip instead of fail, since they were hitting
UNIMPLEMENTED.

BUG=angleproject:1332
BUG=angleproject:1540
BUG=angleproject:1340

Change-Id: Ie3347f2bf2459a5831b66827871998d8fbe7d4b2
Reviewed-on: https://chromium-review.googlesource.com/392490Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>