multimodal model embedding fixes

[libinta]

1. remove scatter_mm_placeholders and gather_mm_placeholders from hpu_model_runner as upstream PR [Core][MM] Optimize encoder cache manager by operating with embeddings only vllm#30475 optimized it
2. add HpuQwen3_VLForConditionalGeneration to use index_copy for _merge_multimodal_embeddings

[github-actions]

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[iboiko-habana]

Please fix basic test
ERROR 12-30 13:48:15 [registry.py:751] File "/usr/local/lib/python3.12/dist-packages/vllm/model_executor/models/qwen3_vl.py", line 41, in <module> ERROR 12-30 13:48:15 [registry.py:751] from transformers.models.qwen3_vl import Qwen3VLProcessor, Qwen3VLVideoProcessor ERROR 12-30 13:48:15 [registry.py:751] File "/usr/local/lib/python3.12/dist-packages/habana_frameworks/torch/core/__init__.py", line 106, in wrapper ERROR 12-30 13:48:15 [registry.py:751] ret = original_fn(*args, **kwargs) ERROR 12-30 13:48:15 [registry.py:751] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ERROR 12-30 13:48:15 [registry.py:751] ModuleNotFoundError: No module named 'transformers.models.qwen3_vl'

[skaulintel]

Please fix basic test ERROR 12-30 13:48:15 [registry.py:751] File "/usr/local/lib/python3.12/dist-packages/vllm/model_executor/models/qwen3_vl.py", line 41, in <module> ERROR 12-30 13:48:15 [registry.py:751] from transformers.models.qwen3_vl import Qwen3VLProcessor, Qwen3VLVideoProcessor ERROR 12-30 13:48:15 [registry.py:751] File "/usr/local/lib/python3.12/dist-packages/habana_frameworks/torch/core/__init__.py", line 106, in wrapper ERROR 12-30 13:48:15 [registry.py:751] ret = original_fn(*args, **kwargs) ERROR 12-30 13:48:15 [registry.py:751] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ERROR 12-30 13:48:15 [registry.py:751] ModuleNotFoundError: No module named 'transformers.models.qwen3_vl'

I believe qwen3_vl only shows up from transformers 4.57.0 onwards. the CI tests seem to be using
transformers 4.55.4

[github-actions]

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[github-actions]

🚧 CI Blocked

The main CI workflow was not started for the following reason:

Your branch is behind the base branch. Please merge or rebase to get the latest changes.