The Vulkan spec explicitly states that "vkCmdBlitImage must not be used
for multisampled source or destination images. Use vkCmdResolveImage for
this purpose." And the only other way to obtain resolve multisample
results is by using resolve attachments as part of a subpass.

This split between blit operations and resolve operations should be
reflected by the Blitter interface so we have less confusion about
its blit() method being used to perform resolves. It will also
facilitate adding a fast path for common resolve operations.

Bug: b/147802090
Change-Id: I2549a5e7acd7ef9ec3f70f8ceb88ff5fc65a0d17
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/47988
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>