Image planes have a distinct meaning in Vulkan, signifying the disjoint
memory regions which store components of a texel format. Typically this
includes YCbCr formats that can have 2 or 3 planes for luminance and
chroma data.

Slices refer to 2D sections of 3D images. Currently we also use slices
for storing each sample of a multisample image separately. Note only
2D images can be multisampled, so there are no 3D images with slices
for the depth and the number of samples.

Bug: b/159210008
Change-Id: I4b70a7b8bb49e79c7494e28aa8280752a5b9727d
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/46288
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>