[Metal] The Metal shader converter is unable to handle the new DXIL vectorized dot product instruction

Nobody has claimed this yet.

Filed a bug with Apple here: https://feedbackassistant.apple.com/feedback/24450317

The following code:

```hlsl
StructuredBuffer X : register(t0);
StructuredBuffer Y : register(t1);
RWStructuredBuffer Out : register(u2);

[numthreads(1,1,1)]
void main() {
vector X5;
vector Y5;
for (uint I = 0; I < 5; ++I) {
X5[I] = X[I];
Y5[I] = Y[I];
}
Out[0] = dot(X5, Y5);
}
```

Causes an abort when compiled with shader model 6.9 (`dxc -T cs_6_9 ...`):
Failed to compile and link DXIL to Metal IR: IRErrorCodeUnsupportedInstruction

This is presumably because of long vector versions of `dx.op.dot`.

Nothing we can do but xfail until this is fixed in the shader converter. This is not technically not a driver bug but does block all Metal runtimes until it is fixed so in practice it is.

Start by locating the offload test that compiles the provided HLSL with dxc -T cs_6_9 and identify how unsupported Metal shader-converter cases are recorded. Reproduce the abort, then mark this vectorized dot-product case as expected to fail until the converter supports the long dx.op.dot instruction; verify that the suite reports the expected failure.

Written by the indexing model from the issue text.