swr: rework resource layout and surface setup

swr: rework resource layout and surface setup

This is a bit of a mega-commit, but unfortunately there's no great way
to break this up since a lot of different pieces have to match up. Here
we do the following:
 - change surface layout to match swr's Load/StoreTile expectations
 - fix sampler settings to respect all sampler view parameters
 - fix stencil sampling to read from secondary resource
 - respect pipe surface format, level, and layer settings
 - fix resource map/unmap based on the new layout logic
 - fix resource map/unmap to copy proper parts of stencil values in and
   out of the matching depth texture

These fix a massive quantity of piglits, including all the
tex-miplevel-selection ones.

Note that the swr native miptree layout isn't extremely space-efficient,
and we end up using it for all textures, not just the renderable ones. A
back-of-the-envelope calculation suggests about 10%-25% increased memory
usage for miptrees, depending on the number of LODs. Single-LOD textures
should be unaffected.

There are a handful of regressions as a result of this change:
 - Some textureGrad tests, these failures match llvmpipe. (There are
   debug settings allowing improved gallivm sampling accurancy.)
 - Some layered clearing tests as swr doesn't currently support that. It
   was getting lucky before because enough other things were broken.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Bruce Cherniak <bruce.cherniak@intel.com>