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/llms/mlflow_ai_gateway.py

@@ -0,0 +1,104 @@
+from __future__ import annotations
+
+import warnings
+from typing import Any, Dict, List, Mapping, Optional
+
+from langchain_core.callbacks import CallbackManagerForLLMRun
+from langchain_core.language_models.llms import LLM
+from langchain_core.pydantic_v1 import BaseModel, Extra
+
+
+# Ignoring type because below is valid pydantic code
+# Unexpected keyword argument "extra" for "__init_subclass__" of "object"
+class Params(BaseModel, extra=Extra.allow):  # type: ignore[call-arg]
+    """Parameters for the MLflow AI Gateway LLM."""
+
+    temperature: float = 0.0
+    candidate_count: int = 1
+    """The number of candidates to return."""
+    stop: Optional[List[str]] = None
+    max_tokens: Optional[int] = None
+
+
+class MlflowAIGateway(LLM):
+    """
+    Wrapper around completions LLMs in the MLflow AI Gateway.
+
+    To use, you should have the ``mlflow[gateway]`` python package installed.
+    For more information, see https://mlflow.org/docs/latest/gateway/index.html.
+
+    Example:
+        .. code-block:: python
+
+            from langchain_community.llms import MlflowAIGateway
+
+            completions = MlflowAIGateway(
+                gateway_uri="<your-mlflow-ai-gateway-uri>",
+                route="<your-mlflow-ai-gateway-completions-route>",
+                params={
+                    "temperature": 0.1
+                }
+            )
+    """
+
+    route: str
+    gateway_uri: Optional[str] = None
+    params: Optional[Params] = None
+
+    def __init__(self, **kwargs: Any):
+        warnings.warn(
+            "`MlflowAIGateway` is deprecated. Use `Mlflow` or `Databricks` instead.",
+            DeprecationWarning,
+        )
+        try:
+            import mlflow.gateway
+        except ImportError as e:
+            raise ImportError(
+                "Could not import `mlflow.gateway` module. "
+                "Please install it with `pip install mlflow[gateway]`."
+            ) from e
+
+        super().__init__(**kwargs)
+        if self.gateway_uri:
+            mlflow.gateway.set_gateway_uri(self.gateway_uri)
+
+    @property
+    def _default_params(self) -> Dict[str, Any]:
+        params: Dict[str, Any] = {
+            "gateway_uri": self.gateway_uri,
+            "route": self.route,
+            **(self.params.dict() if self.params else {}),
+        }
+        return params
+
+    @property
+    def _identifying_params(self) -> Mapping[str, Any]:
+        return self._default_params
+
+    def _call(
+        self,
+        prompt: str,
+        stop: Optional[List[str]] = None,
+        run_manager: Optional[CallbackManagerForLLMRun] = None,
+        **kwargs: Any,
+    ) -> str:
+        try:
+            import mlflow.gateway
+        except ImportError as e:
+            raise ImportError(
+                "Could not import `mlflow.gateway` module. "
+                "Please install it with `pip install mlflow[gateway]`."
+            ) from e
+
+        data: Dict[str, Any] = {
+            "prompt": prompt,
+            **(self.params.dict() if self.params else {}),
+        }
+        if s := (stop or (self.params.stop if self.params else None)):
+            data["stop"] = s
+        resp = mlflow.gateway.query(self.route, data=data)
+        return resp["candidates"][0]["text"]
+
+    @property
+    def _llm_type(self) -> str:
+        return "mlflow-ai-gateway"