[Bugfix] Fix missing sequence_lengths in EXAONE-4.5 vision encoder

[appleparan]

Purpose

PR #42787 made the Qwen2.5-VL vision backbone pass sequence_lengths (FlashInfer CuDNN metadata) to every vision block, but the EXAONE-4.5 overrides of the vision block and attention kept the pre-#42787 signature. Since EXAONE-4.5 inherits Qwen2_5_VisionTransformer.forward, any multimodal request now fails with:

TypeError: Exaone4_5_VisionBlock.forward() got an unexpected
keyword argument 'sequence_lengths'

Thread sequence_lengths through Exaone4_5_VisionBlock and EXAONE4_5_VisionAttention into MMEncoderAttention, and register it in the block's dynamic_arg_dims for torch.compile, mirroring the equivalent fix for qwen3_omni_moe_thinker in #35741.

Closes #45071

Test Plan

• pre-commit run --files vllm/model_executor/models/exaone4_5.py
  (ruff check/format, mypy, typos, SPDX)
• Deploy vllm/vllm-openai:v0.22.0 with the patched file overlaid on
  2x A100, using the reproduce command from [Bug]: EXAONE-4.5 Vision — unexpected keyword argument 'sequence_lengths' in Exaone4_5_VisionBlock.forward() #45071, and confirm the
  server completes startup profiling and serves image requests

Test Result

• pre-commit: all hooks passed
• Server startup + image inference: It worked

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