Implementation will follow.

Bug: b/132437008
Tests: dEQP-VK.*ycbcr*
Change-Id: I5fd4826257c6886e109d007ac926ee61895bf62d
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/31613
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>