MSL doesn't seem to have any special handling for undefined values,
differently from SPIR-V. Thus we just emit zeros.
UNDEF registers are sometimes created by the DXIL parser,
for example in sm6_parser_emit_composite_construct().
Adjust the algorithm for deciding for which profiles to test compilation.
We first ensure that if the compilation result changes (most often as the result
of a feature introduced in a specific version), we test the versions immediately
on either side of the change, to validate that vkd3d-shader is emulating the
same version behaviour.
We then ensure that we are testing at least one version from each set of sm1,
sm4, and sm6.
This is simply unnecessary and wastes time.
As part of this, simply remove the "all" directive. Only for a couple of tests
is it even potentially interesting to validate all pixels (e.g.
nointerpolation.shader_test), and for those "all" is replaced with an explicit
(0, 0, 640, 480) rect.
In all other cases we just probe (0, 0).
