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/email.py

@@ -0,0 +1,117 @@
+import os
+from typing import Any, List
+
+from langchain_core.documents import Document
+
+from langchain_community.document_loaders.base import BaseLoader
+from langchain_community.document_loaders.unstructured import (
+    UnstructuredFileLoader,
+    satisfies_min_unstructured_version,
+)
+
+
+class UnstructuredEmailLoader(UnstructuredFileLoader):
+    """Load email files using `Unstructured`.
+
+    Works with both
+    .eml and .msg files. You can process attachments in addition to the
+    e-mail message itself by passing process_attachments=True into the
+    constructor for the loader. By default, attachments will be processed
+    with the unstructured partition function. If you already know the document
+    types of the attachments, you can specify another partitioning function
+    with the attachment partitioner kwarg.
+
+    Example
+    -------
+    from langchain_community.document_loaders import UnstructuredEmailLoader
+
+    loader = UnstructuredEmailLoader("example_data/fake-email.eml", mode="elements")
+    loader.load()
+
+    Example
+    -------
+    from langchain_community.document_loaders import UnstructuredEmailLoader
+
+    loader = UnstructuredEmailLoader(
+        "example_data/fake-email-attachment.eml",
+        mode="elements",
+        process_attachments=True,
+    )
+    loader.load()
+    """
+
+    def __init__(
+        self, file_path: str, mode: str = "single", **unstructured_kwargs: Any
+    ):
+        process_attachments = unstructured_kwargs.get("process_attachments")
+        attachment_partitioner = unstructured_kwargs.get("attachment_partitioner")
+
+        if process_attachments and attachment_partitioner is None:
+            from unstructured.partition.auto import partition
+
+            unstructured_kwargs["attachment_partitioner"] = partition
+
+        super().__init__(file_path=file_path, mode=mode, **unstructured_kwargs)
+
+    def _get_elements(self) -> List:
+        from unstructured.file_utils.filetype import FileType, detect_filetype
+
+        filetype = detect_filetype(self.file_path)
+
+        if filetype == FileType.EML:
+            from unstructured.partition.email import partition_email
+
+            return partition_email(filename=self.file_path, **self.unstructured_kwargs)
+        elif satisfies_min_unstructured_version("0.5.8") and filetype == FileType.MSG:
+            from unstructured.partition.msg import partition_msg
+
+            return partition_msg(filename=self.file_path, **self.unstructured_kwargs)
+        else:
+            raise ValueError(
+                f"Filetype {filetype} is not supported in UnstructuredEmailLoader."
+            )
+
+
+class OutlookMessageLoader(BaseLoader):
+    """
+    Loads Outlook Message files using extract_msg.
+
+    https://github.com/TeamMsgExtractor/msg-extractor
+    """
+
+    def __init__(self, file_path: str):
+        """Initialize with a file path.
+
+        Args:
+            file_path: The path to the Outlook Message file.
+        """
+
+        self.file_path = file_path
+
+        if not os.path.isfile(self.file_path):
+            raise ValueError("File path %s is not a valid file" % self.file_path)
+
+        try:
+            import extract_msg  # noqa:F401
+        except ImportError:
+            raise ImportError(
+                "extract_msg is not installed. Please install it with "
+                "`pip install extract_msg`"
+            )
+
+    def load(self) -> List[Document]:
+        """Load data into document objects."""
+        import extract_msg
+
+        msg = extract_msg.Message(self.file_path)
+        return [
+            Document(
+                page_content=msg.body,
+                metadata={
+                    "source": self.file_path,
+                    "subject": msg.subject,
+                    "sender": msg.sender,
+                    "date": msg.date,
+                },
+            )
+        ]