Correctly deal with GPU written depth_stencil textures.
Correctly deal with GPU written depth_stencil textures.

Since we cannot actually readback stencil data, simply clear it to
zeros in the conversion.

pmuetschard/gapid,google/agi,google/agi,pmuetschard/gapid,pmuetschard/gapid,google/agi,google/gapid,pmuetschard/gapid,google/gapid,google/gapid,pmuetschard/gapid,pmuetschard/gapid,google/gapid,google/gapid,google/gapid,google/agi,google/agi,pmuetschard/gapid,google/agi,google/agi,pmuetschard/gapid,google/agi,google/gapid,google/gapid