Vulkan: Enable EXT_frag_depth
Vulkan: Enable EXT_frag_depth

Natively supported with GLES3 dEQP tests already enabled and passing.

Bug: angleproject:3218
Change-Id: I5ff94e3b16d2025a58d5a448383049f9330dd46f
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1600864
Commit-Queue: Shahbaz Youssefi <582eeec4f08a2ccd61e3ef52115e6e7c571582de@chromium.org>
Reviewed-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>

ppy/angle,ppy/angle,ppy/angle,ppy/angle