The main aim of this CL is to add tests for SetViewport. But it
also implements the feature on Vulkan backend to verify the tests.
BUG=dawn:53
TEST=dawn_end2end_tests
Change-Id: I9578b2d9650cb952ce67cf91f79e9682c9932ee3
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/8820
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Yunchao He <yunchao.he@intel.com>