CUDA MatMulNBits: make SM90 prepacked rejection order portable and stabilize test match prefix

[Copilot]

Description

MatMulNBits.Fp16_Int4_PrepackedSm90BlockSize32Rejected was failing in CUDA Plugin Linux CI because SM90 prepacked validation emitted environment-dependent messages before checking runner capability.
This change makes rejection precedence portable across runner/build-machine combinations and stabilizes message matching via a shared prefix.

• Runtime-first SM90 gating

  • For weight_prepacked=2 (SM90 layout), validation now checks sm_ == 90 before compile-time native-SM90 availability checks.

• Stable rejection prefix contract

  • All SM90-prepacked rejection paths now use the exact prefix:
    • weight_prepacked=2 (SM90 layout)

• Build-support error clarity

  • If COMPILE_HOPPER_TMA_GEMMS is unavailable, the post-runtime-check error explicitly reports missing native SM90 Hopper support.

• Block-size rule preserved

  • SM90 prepacked still enforces block_size ∈ {64, 128} after runtime/build checks.

• Test portability update

  • Fp16_Int4_PrepackedSm90BlockSize32Rejected continues asserting only the stable shared prefix so it passes on:
    • non-SM90 runners,
    • SM90 runners without native TMA support in the build,
    • SM90 runners with native TMA support (block-size rejection path).

if (weight_prepacked_ == kMatMulNBitsWeightPrepackedSm90) {
  ORT_ENFORCE(sm_ == 90, "weight_prepacked=2 (SM90 layout) ...");
#if !defined(COMPILE_HOPPER_TMA_GEMMS)
  ORT_THROW("weight_prepacked=2 (SM90 layout) is not supported by this ONNX Runtime build ...");
#endif
  ORT_ENFORCE(block_size_ == 64 || block_size_ == 128,
              "weight_prepacked=2 (SM90 layout) supports block_size 64 or 128 only, but got ", block_size_);
}

Motivation and Context

The failing CI test exposed that rejection order for SM90-prepacked weights depended on build configuration rather than first honoring runtime device capability, which is incorrect for SM90 layout execution on non-SM90 runners.
This update aligns validation precedence with execution constraints and makes test matching architecture-agnostic while preserving precise downstream rejection semantics.

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