Add tests for MoE dispatch and Triton qzeros reshape

[wjabbour]

Purpose

CompressedTensorsMoEMethod.get_moe_method is pure routing logic — given a quantization scheme (and platform/config state for the ROCm branches), it picks one of ~9 backend MoE method classes — but had no direct test coverage. This is especially risky on the ROCm paths, where selection depends on a 7-term AND (native RDNA kernel vs. gfx950 FlyDSL vs. emulation fallback); a single dropped term would silently misroute production traffic to the wrong kernel.

Adds two test files:

• tests/kernels/moe/test_compressed_tensors_moe_dispatch.py — 26 tests covering scheme resolution, simple and weight/input backend routing, NVFP4 routing, and the three ROCm sub-branches inside the wNa16 path (including a parametrized check that the gfx950/FlyDSL route's 7-term AND requires every term individually). Every backend class is mocked, so these assert routing only — which class gets selected and with what arguments — not internal behavior. Runs on CPU, no GPU/model dependency.
• tests/kernels/quantization/test_wna16_moe_triton_gptq_qzeros.py — 2 regression tests locking in that AutoGPTQ/compressed-tensors w13/w2 zero-points get transposed and reshaped from the checkpoint's K-first int32 layout into the N-first, packed-uint8 layout fused_moe_kernel_gptq_awq expects — the weights and scales already got this transform; this closes the gap for zero-points. Pure tensor-shape/dtype test, no GPU/Triton kernel launch.

Related PRs and discussions:

vllm-project#44570 (comment)
vllm-project#44570
vllm-project#52112
vllm-project#53629 (RFC)

This PR was made in assistance with Claude but I reviewed every line.

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[wjabbour]

Opened against the wrong base — this was meant to target vllm-project/vllm upstream, not my own fork. Closing; opening the real PR now.