[Bug 54887] Add support for SampleGrad() function

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=54887

--- Comment #1 from Henri Verbeet  ---
(In reply to Ethan Lee from comment #0)
> Amusingly, there's a test in vkd3d already, it's just in binary form only!

As you might have noticed, we have a bunch of those. Most of those predate HLSL
support in vkd3d-shader. We'd like to get rid of those embedded binary shaders
and replace them with their HLSL source, but it hasn't been a top priority so
far.