[Feature]: Remove the autotuner invocation from AD's nvfp4_gemm operator

[nzmora-nvidia]

🚀 The feature, motivation and pitch

The autotuner is used when AD record cuda-graphs, and per-shape tactics are cached.
The operator should not explicitly use the auto-tuner context because that is the responsibility of the AD engine.
TRTLLM's nvfp4_gemm_runner is responsible for auto-tuning and caching a tactic and uses this tactic during inference, but only if the auto-tuner is not inside an auto-tuner context.

Alternatives

No response

Additional context

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