This patch adds the support of dot4I8Packed and dot4U8Packed in
semantics under the extension "chromium_experimental_dp4a".
Bug: tint:1497
Test: tint_unittests
Change-Id: I659172fcb8953ba13b49664c6c9ad75724ff5957
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/88962
Commit-Queue: Jiawei Shao <jiawei.shao@intel.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>