community[patch]: Add Support for GPU Index Types in Milvus 2.4 (#19468)

- **Description:** This commit introduces support for the newly
available GPU index types introduced in Milvus 2.4 within the LangChain
project's `milvus.py`. With the release of Milvus 2.4, a range of
GPU-accelerated index types have been added, offering enhanced search
capabilities and performance optimizations for vector search operations.
This update ensures LangChain users can fully utilize the new
performance benefits for vector search operations.
    - Reference: https://milvus.io/docs/gpu_index.md

Co-authored-by: Bagatur <22008038+baskaryan@users.noreply.github.com>

libs/community/langchain_community/vectorstores/milvus.py

@@ -156,6 +156,18 @@ class Milvus(VectorStore):
             "ANNOY": {"metric_type": "L2", "params": {"search_k": 10}},
             "SCANN": {"metric_type": "L2", "params": {"search_k": 10}},
             "AUTOINDEX": {"metric_type": "L2", "params": {}},
+            "GPU_CAGRA": {
+                "metric_type": "L2",
+                "params": {
+                    "itopk_size": 128,
+                    "search_width": 4,
+                    "min_iterations": 0,
+                    "max_iterations": 0,
+                    "team_size": 0,
+                },
+            },
+            "GPU_IVF_FLAT": {"metric_type": "L2", "params": {"nprobe": 10}},
+            "GPU_IVF_PQ": {"metric_type": "L2", "params": {"nprobe": 10}},
         }
 
         self.embedding_func = embedding_function