Rotation is now handled in the shader compiler with specialization
constant, it should be removed from driver uniforms. Since Metal is
using the flipXY, flipXY/negFlipXY are still kept in the shader side
implementation, but have moved to TranslatorMetal in this CL.

Bug: b/171750979
Change-Id: Ie8d15ef227cb52a6e19e4319ecc9f09bda42e667
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2519863Reviewed-by: Ian Elliott <ianelliott@google.com>
Reviewed-by: Tim Van Patten <timvp@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Charlie Lao <cclao@google.com>