The patch refactors the tests to use the GL RAII objects from
gl_raii.h. It also specifies a correct internal format for a texture 2D
array object in one of the tests so that the texture is
color-renderable.

BUG=angleproject:2062
TEST=angle_end2end_tests

Change-Id: Ie536ffeb5b2f2594f5273b795fe786a5042f63d4
Reviewed-on: https://chromium-review.googlesource.com/603610
Commit-Queue: Martin Radev <mradev@nvidia.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Olli Etuaho <oetuaho@nvidia.com>