WIP: llvmpipe/fs: fix multisample depth/stencil fs writes.
The state wasn't storing the shader depth/stencil outputs per-sample, so only the last sample emitted was being used for the late depth test and stencil ref.
Noticed while trying to fix some vulkan depth stencil resolve issues
Fixes: a0195240 ("llvmpipe: handle multisample early depth test/late depth write")