turnip: implement variableMultisampleRate
requested to merge Danil/mesa:turnip/fix/msaa-state-should-depend-on-rasterizationSamples into master
If subpass doesn't have depth/color attachments - samples count is
devised from VkPipelineMultisampleStateCreateInfo::rasterizationSamples.
Without variableMultisampleRate enabled all pipelines in such subpass
should have the same samples count; variableMultisampleRate allows
to have pipelines with different number of samples in one subpass,
given that it doesn't have depth/color attachments.
Blob doesn't have it enabled but there is no known reason for this.
Passes:
dEQP-VK.pipeline.multisample.variable_rate.*Fixes test:
dEQP-VK.pipeline.framebuffer_attachment.no_attachments_ms