community[major], core[patch], langchain[patch], experimental[patch]: Create langchain-community (#14463)

Moved the following modules to new package langchain-community in a backwards compatible fashion:

```
mv langchain/langchain/adapters community/langchain_community
mv langchain/langchain/callbacks community/langchain_community/callbacks
mv langchain/langchain/chat_loaders community/langchain_community
mv langchain/langchain/chat_models community/langchain_community
mv langchain/langchain/document_loaders community/langchain_community
mv langchain/langchain/docstore community/langchain_community
mv langchain/langchain/document_transformers community/langchain_community
mv langchain/langchain/embeddings community/langchain_community
mv langchain/langchain/graphs community/langchain_community
mv langchain/langchain/llms community/langchain_community
mv langchain/langchain/memory/chat_message_histories community/langchain_community
mv langchain/langchain/retrievers community/langchain_community
mv langchain/langchain/storage community/langchain_community
mv langchain/langchain/tools community/langchain_community
mv langchain/langchain/utilities community/langchain_community
mv langchain/langchain/vectorstores community/langchain_community
mv langchain/langchain/agents/agent_toolkits community/langchain_community
mv langchain/langchain/cache.py community/langchain_community
mv langchain/langchain/adapters community/langchain_community
mv langchain/langchain/callbacks community/langchain_community/callbacks
mv langchain/langchain/chat_loaders community/langchain_community
mv langchain/langchain/chat_models community/langchain_community
mv langchain/langchain/document_loaders community/langchain_community
mv langchain/langchain/docstore community/langchain_community
mv langchain/langchain/document_transformers community/langchain_community
mv langchain/langchain/embeddings community/langchain_community
mv langchain/langchain/graphs community/langchain_community
mv langchain/langchain/llms community/langchain_community
mv langchain/langchain/memory/chat_message_histories community/langchain_community
mv langchain/langchain/retrievers community/langchain_community
mv langchain/langchain/storage community/langchain_community
mv langchain/langchain/tools community/langchain_community
mv langchain/langchain/utilities community/langchain_community
mv langchain/langchain/vectorstores community/langchain_community
mv langchain/langchain/agents/agent_toolkits community/langchain_community
mv langchain/langchain/cache.py community/langchain_community
```

Moved the following to core
```
mv langchain/langchain/utils/json_schema.py core/langchain_core/utils
mv langchain/langchain/utils/html.py core/langchain_core/utils
mv langchain/langchain/utils/strings.py core/langchain_core/utils
cat langchain/langchain/utils/env.py >> core/langchain_core/utils/env.py
rm langchain/langchain/utils/env.py
```

See .scripts/community_split/script_integrations.sh for all changes

libs/community/langchain_community/document_loaders/mongodb.py

@@ -0,0 +1,77 @@
+import asyncio
+import logging
+from typing import Dict, List, Optional
+
+from langchain_core.documents import Document
+
+from langchain_community.document_loaders.base import BaseLoader
+
+logger = logging.getLogger(__name__)
+
+
+class MongodbLoader(BaseLoader):
+    """Load MongoDB documents."""
+
+    def __init__(
+        self,
+        connection_string: str,
+        db_name: str,
+        collection_name: str,
+        *,
+        filter_criteria: Optional[Dict] = None,
+    ) -> None:
+        try:
+            from motor.motor_asyncio import AsyncIOMotorClient
+        except ImportError as e:
+            raise ImportError(
+                "Cannot import from motor, please install with `pip install motor`."
+            ) from e
+        if not connection_string:
+            raise ValueError("connection_string must be provided.")
+
+        if not db_name:
+            raise ValueError("db_name must be provided.")
+
+        if not collection_name:
+            raise ValueError("collection_name must be provided.")
+
+        self.client = AsyncIOMotorClient(connection_string)
+        self.db_name = db_name
+        self.collection_name = collection_name
+        self.filter_criteria = filter_criteria or {}
+
+        self.db = self.client.get_database(db_name)
+        self.collection = self.db.get_collection(collection_name)
+
+    def load(self) -> List[Document]:
+        """Load data into Document objects.
+
+        Attention:
+
+        This implementation starts an asyncio event loop which
+        will only work if running in a sync env. In an async env, it should
+        fail since there is already an event loop running.
+
+        This code should be updated to kick off the event loop from a separate
+        thread if running within an async context.
+        """
+        return asyncio.run(self.aload())
+
+    async def aload(self) -> List[Document]:
+        """Load data into Document objects."""
+        result = []
+        total_docs = await self.collection.count_documents(self.filter_criteria)
+        async for doc in self.collection.find(self.filter_criteria):
+            metadata = {
+                "database": self.db_name,
+                "collection": self.collection_name,
+            }
+            result.append(Document(page_content=str(doc), metadata=metadata))
+
+        if len(result) != total_docs:
+            logger.warning(
+                f"Only partial collection of documents returned. Loaded {len(result)} "
+                f"docs, expected {total_docs}."
+            )
+
+        return result