i965: Support array_layout == ALL_SLICES_AT_EACH_LOD for multiple LODs

i965: Support array_layout == ALL_SLICES_AT_EACH_LOD for multiple LODs

Previously array_layout ALL_SLICES_AT_EACH_LOD was only used for array
spacing lod0 on gen7+ and therefore was only used with a single mip
level.

gen6 separate stencil & hiz only support LOD0, so we need to allocate
the miptree similar to gen7+ array spacing lod0, except we also need
space for multiple mip levels. (Since OpenGL stencil and depth support
multiple LODs.)

The miptree is allocated with tightly packed array slice spacing, but
we still also pack the miplevels into the region similar to a normal
multi mip level packing.

A 2D Array texture with 2 slices and multiple LODs would look somewhat
like this:

+----------+
|          |
|          |
+----------+
|          |
|          |
+----------+
+---+ +-+
|   | +-+
+---+ +-+
|   | :
+---+

v3:
 * Use new array_layout enum
 * ASCII art!

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Acked-by: Kenneth Graunke <kenneth@whitecape.org>