d3d10umd,d3d10sw: Initial import.

This change adds a gallium D3D10 state tracker that works as a WDDM UMD
software driver, similar to Microsoft WARP, but using llvmpipe/softpipe.

The final deliverable is a d3d10sw.dll, which is similar to WARP's
d3d10warp.dll.

This has been used to run Microsoft Windows HCK wgf11* tests with
llvmpipe, and they were at one point passing 100%.

Known limitations:
- TGSI (no NIR)
- D3D10 only (no D3D11 support yet)
- no WINE integration (WINE doesn't implement WDDM DDI.)

For further details see:
- src/gallium/frontends/d3d10umd/README.md
- src/gallium/targets/d3d10sw/README.md

v2: Drop the DXBC-based disassembly.  Add missing break statements.
v3: Incorporate Jesse's feedback.

Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Acked-by: Jesse Natalie <jenatali@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10687>

meson_options.txt

@@ -142,6 +142,12 @@ option(
   value : false,
   description : 'build gallium "nine" Direct3D 9.x frontend.',
 )
+option(
+  'gallium-d3d10umd',
+  type : 'boolean',
+  value : false,
+  description : 'build gallium D3D10 WDDM UMD frontend.',
+)
 option(
   'gallium-opencl',
   type : 'combo',