Use maximum number of batched tokens to autotune MoE

[nvjullin]

Purpose

Follow up on #27904.
CC @varun-sundar-rabindranath.

Test Plan

Test Result

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[gemini-code-assist]

Code Review

This pull request updates the Mixture-of-Experts (MoE) autotuning logic to use the maximum number of batched tokens from the scheduler configuration, which is a more appropriate parameter for this purpose than the CUDA graph capture size. The changes are logical, but the refactoring is incomplete, leading to a critical issue where a removed attribute is still being accessed in the code.

[chatgpt-codex-connector]

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[nvpohanh]

@nvjullin could you rebase so that we can keep driving this PR? thanks