Reland "Check FP16 support on vulkan backend"

This reverts commit 0357eed7de
and reland commit bdc05c3d5f.

The Vulkan-Loader has a bug where if the instance is created
with Vulkan 1.1 and not the promoted extensions, it will skip
emulation and if the ICD doesn't support Vulkan 1.1 nor the
extensions. Enable the promoted extensions, even when creating
a Vulkan 1.1 instance.

Original change's description:
> Check FP16 support on vulkan backend
>
> This patch check FP16 support on vulkan backend, and introduces
> the shader_float16 extension.
>
> BUG=dawn:426
> TEST=dawn_end2end_tests
>
> Change-Id: Ie09568a416ce9eb2c11afeede3e7da520550d5fb
> Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/21901
> Commit-Queue: Xinghua Cao <xinghua.cao@intel.com>
> Reviewed-by: Corentin Wallez <cwallez@chromium.org>
> Reviewed-by: Jiawei Shao <jiawei.shao@intel.com>
> Reviewed-by: Kai Ninomiya <kainino@chromium.org>
> Reviewed-by: Austin Eng <enga@chromium.org>

Bug: chromium:1087896, dawn:426
Change-Id: I2c4465fb2fe957966b44d3e5840112219481c639
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/22781
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

src/tests/DawnTest.cpp

@@ -1144,6 +1144,7 @@ namespace detail {
     }
 
     template class ExpectEq<uint8_t>;
+    template class ExpectEq<uint16_t>;
     template class ExpectEq<uint32_t>;
     template class ExpectEq<RGBA8>;
     template class ExpectEq<float>;