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feat

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feat(milvus2): 新增 milvus2 indexer 和 retriever 组件

(Optional) More detailed description for this PR(en: English/zh: Chinese).

en:
This PR introduces new Milvus 2.x components (indexer and retriever) under components/indexer/milvus2 and components/retriever/milvus2, using the latest milvus-io/milvus/client/v2 SDK.

Indexer Features:

• Auto Management: automatically handles collection schema creation, index building, and loading.
• Comprehensive Index Support: Auto, HNSW, IVF (Flat, PQ, SQ8), RaBitQ (2.6+), FLAT, DiskANN, SCANN, and GPU Indexes (BruteForce, IVF_Flat, IVF_PQ, Cagra).
• Hybrid Search Ready: Native support for Sparse Vectors (BM25/SPLADE) alongside Dense Vectors.
• Service-side Processing: Support for Milvus Functions (e.g., auto-generating sparse vectors via BM25) and Analyzers.
• Flexible Data Handling: Dynamic schema support and custom document-to-column conversion.

Retriever Features:

• Multiple Search Modes: Approximate, Range, Hybrid (Dense + Sparse with RRF), Iterator, and Scalar search.
• Advanced Filtering: Support for score thresholds, range filters, and metadata filtering.
• Result Customization: Grouping support and custom result-to-document conversion.

Examples included:

• Indexer: demo, hnsw, ivf_flat, rabitq, auto, diskann, hybrid (sparse), byov.
• Retriever: approximate, range, hybrid (dense+sparse), iterator, scalar, grouping, filtered.

zh:
本 PR 在 components/indexer/milvus2 和 components/retriever/milvus2 目录下引入了基于最新 milvus-io/milvus/client/v2 SDK 的 Milvus 2.x 组件（indexer 和 retriever）。

Indexer 特性：

• 自动管理：自动处理集合 Schema 创建、索引构建和加载。
• 全面的索引支持：支持 Auto、HNSW、IVF (Flat, PQ, SQ8)、RaBitQ (2.6+)、FLAT、DiskANN、SCANN 以及 GPU 索引 (BruteForce, IVF_Flat, IVF_PQ, Cagra)。
• 混合搜索就绪：原生支持稀疏向量 (BM25/SPLADE) 与稠密向量共存。
• 服务端处理：支持 Milvus Functions（如通过 BM25 自动生成稀疏向量）和 Analyzers（分词器）。
• 灵活的数据处理：支持动态 Schema 和自定义文档到列的转换。

Retriever 特性：

• 多种搜索模式：Approximate、Range、Hybrid (Dense + Sparse with RRF)、Iterator 和 Scalar 搜索。
• 高级过滤：支持分数阈值、范围过滤和元数据过滤。
• 结果定制：支持分组 (Grouping) 和自定义结果到文档的转换。

包含示例：

• Indexer: demo, hnsw, ivf_flat, rabitq, auto, diskann, hybrid, byov.
• Retriever: approximate, range, hybrid, iterator, scalar, grouping, filtered.

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