Multisample images can be copied to other multisample images with the
same number of samples, without undergoing multisample resolve.

We were using the Blitter::copy() code path both for vkCmdCopyImage and
attachment resolve operations at the end of subpasses, leading to
resolve operations happening on copy commands. They are now detangled
and copy() is able to handle multiple samples the same way as 3D
slices.

Bug: b/159210008
Change-Id: I4c285ca7ca58e9f8c6cf7bd942041e038b042cb9
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/46129
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>