Lots of these tests aren't actually testing malformed shaders, so the
name was misleading. ShaderValidationTest reflects the content of the
tests better.

Some test classes that needlessly used different API spec versions are
also merged.

BUG=angleproject:1673
TEST=angle_unittests

Change-Id: Ib842af153a09d3887f9bb857709fd0cd29bcc9c4
Reviewed-on: https://chromium-review.googlesource.com/422368Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>