Fix MoE decode optimization for experts living in a submodel
Author: IlyasMoutawwakil
Pull request: yes

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`_optimize_model_for_decode` only inspected the top-level config's `_experts_implementation`, so it never switched grouped_mm -> batched_mm for MoE that lives in a submodel (e.g. a VLM's `text_config`). Add `get_experts_implementation()` to snapshot the implementation across the model and every sub_config, and drive a dict-based switch that `set_experts_implementation` recurses. Un-skip the two glm4v_moe decode tests this makes pass.

# What does this PR do?

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Fixes # (issue)

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The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_47107). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

**[For maintainers]** Suggested jobs to run (before merge)

run-slow: glm4v_moe, hunyuan_v1_moe, kimi_k25

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### CI recap

**Dashboard:** [View test results in Grafana](https://transformers-ci.lor-e.huggingface.cool/d/pytest-observability-by-pr/pytest-observability-branch?var-pr=47107)
**Latest run:** [28880677434:1](https://github.com/huggingface/transformers/actions/runs/28880677434)
**Result:** `success` | **Jobs:** 15 | **Tests:** 172,652 | **Failures:** 0 | **Duration:** 18h 42m

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