If a user is performing a blit to resolve a multisample color buffer
into a single attachment, ANGLE can use subpass resolve attachments to
resolve directly into the destination buffer as part of the render pass.
This allows the data to remain in tiler memory and reduce the extra
bandwidth required to write the multisampled data back to perform the
copy.

This work also requires restoring/reopening a render pass if it has been
finished already, assuming the finished render pass was started and for
the framebuffer that is the source for the blit command. Other objects
that were created when the render pass was started need to be updated as
well, such as the source FramebufferVk's resolve attachment, the
CommandBufferHelper's vk::Framebuffer and vk::RenderPassDesc, etc.

While this is better than performing vkCmdResolveImage(), there is still
another major part of optimizing MSAA using resolve attachments not
implemented here: discarding the multisampled image rather than writing
it to GMEM, which requires the user to invalidate the read FBO after the
blit.

This CL was verified with AGI to make sure there are no explicit blits
to resolve the multiple sampled image.

Bug: b/159903491
Test: FramebufferTest_ES31.*Blit*
Test: VulkanPerformanceCounterTest_ES31.MultisampleResolveWithBlit
Change-Id: I320a26088d8f614a295e7feec275d71310391806
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2298663
Commit-Queue: Tim Van Patten <timvp@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Charlie Lao <cclao@google.com>