[V1][Bugfix] Fix data item ordering in mixed-modality inference

[ywang96]

Due to v1 re-arch and design of get_input_embeddings being not modality-aware, the order of embeddings in encoder_outputs needs to match the order of multimodal inputs (MultiModalKwargs) in the current batch.

However, batching MultiModalKwargs when there are multiple modalities in the same batch will not preserve their original order, and this PR adds a temporary workaround for this issue.

[github-actions]

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[DarkLight1337]

LGTM if you don't plan to change https://github.com/vllm-project/vllm/pull/12259/files#r1923428521