[HLSL] Extend LinAlg exec test shapes and types

[Jack Elliott (JoeCitizen)]

Several LinAlg exec checks only ran at shapes below the usual native tile size, and Tier 1 I8/U8 support had little or no coverage. This adds tests at native granularity and fills the I8/U8 gaps.

• Wave F16 multiply at 16x16x8, and I8/U8 to I32 at 16x32x8 and 32x32x32.
• ThreadGroup multiply and load/store at fixed 128 and 256 thread groups. I8/U8 use 32x32x32 at 128 threads so K stays at 32.
• F32 element access, layout round trips and I32/F32 contention on 16x16 and 16x32 accumulators, plus F32 accumulator to F16 A/B casts.
• WaveScaled ThreadGroup load/store now sweeps group sizes.
• Mandatory I8/U8 vector Convert tests: saturation, rounding, inf/NaN, a partial last word, and Convert feeding a MatVec.

All new matmul cases stay capability gated. Tested on WARP built from current Direct3D main: all new cases pass except the two I32 contention cases, which skip because I32 atomic accumulate isn't advertised.

Fixes #9047

[Copilot]

🟢 Approval recommended

Static review found no blocking issues in the test-only changes, capability gating, or expected-result checks.

No open issues 🎉

What changed in this PR

Expands LinAlg execution coverage to address #9047, using hardware-relevant shapes and covering required I8/U8 conversions.

Changes:

• Adds capability-gated Wave and fixed-size ThreadGroup matrix tests.
• Extends F32 element access, layout, contention, and cast coverage.
• Adds packed-byte conversion edge cases and Convert-to-MatVec tests.

File	Description
tools/​clang/​unittests/​HLSLExec/​LinAlgTests.cpp	Extends test shapes, types, conversion checks, and supporting helpers.

_{Review effort: Balanced}