Enables reading from multisampled input attachments and storage images

Bug: b/131171141
Test: dEQP-VK.renderpass.*.multisample.*
Change-Id: I719d54c31eb12f58ba7fbdd614ecf3073bfc6d40
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/30553
Presubmit-Ready: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Chris Forbes <chrisforbes@google.com>