The renderFormat is only ever needed in renderer11_utils when
determining which multisample sample counts a format supports.
Determine the renderFormat in the context where it is needed instead
of storing it in the TextureFormat structure. Extra fallbacks can
also be removed from the code.

The D3D11FormatTablesTest is restructured so that it doesn't need to
use the renderFormat field.

This refactoring is done to make it simpler to expand usage of the
ANGLE format enumeration in the C++ code.

BUG=angleproject:1244
TEST=angle_end2end_tests,
     dEQP-GLES3.functional.fbo.* (no regressions)

Change-Id: I980152eb2f3fdaaa1cc5b08e3c9b695c1625e9e5
Reviewed-on: https://chromium-review.googlesource.com/328680Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>