[Feature] Support evaluating selected dataset indices

[reacher-z]

Summary

• add --data-indices as a JSON mapping from dataset names to sample indices
• apply the subset consistently in local, distributed, and async API modes
• keep video pack metadata and reused prediction/checkpoint files scoped to the selected samples
• avoid reusing full-dataset evaluation auxiliary files for subset runs
• document the option in the English and Chinese quickstarts

This lets users rerun a few problematic samples without rebuilding a custom dataset. Unknown datasets, missing indices, invalid values, and duplicates fail explicitly instead of being silently skipped.

python run.py --data MMBench_DEV_EN --data-indices '{"MMBench_DEV_EN": [1203, 63384]}' --model qwen_chat

Closes #1474.

Tests

• python -m unittest discover -s tests -p 'test_dataset_subset.py'
• python tests/test_inference_api.py TestInferenceApiProcessHelpers.test_load_checkpoint_ignores_results_outside_dataset_subset
• pre-commit run --files run.py vlmeval/inference_api.py vlmeval/utils/dataset_subset.py tests/test_dataset_subset.py tests/test_inference_api.py docs/en/Quickstart.md docs/zh-CN/Quickstart.md

AI assistance

Implementation and tests were prepared with OpenAI Codex assistance and manually validated before submission.