[executorch][serialization] Data serialization interface

Pull Request resolved: #7194

Introduce data serialization interface.
ghstack-source-id: 256825077
@exported-using-ghexport

Differential Revision: [D65947145](https://our.internmc.facebook.com/intern/diff/D65947145/)

Author: lucylq

exir/_serialize/data_serializer.py

@@ -0,0 +1,53 @@
+from abc import ABC, abstractmethod
+from typing import Dict, List, Tuple, Union
+
+from executorch.exir._serialize._cord import Cord
+
+from executorch.exir.schema import Tensor
+
+
+# Abstract base class that data serializers should adhere to.
+class DataSerializer(ABC):
+    @abstractmethod
+    def __init__(self) -> None:
+        """
+        This initializer may be overridden in derived classes to hold
+        the data required for serialization, eg. configurations.
+        """
+        pass
+
+    @abstractmethod
+    def serialize_tensors(
+        self,
+        tensor_buffer: List[bytes],
+        tensor_map: Dict[str, int],
+        tensor_metadata: Dict[str, Tensor],
+    ) -> Union[Cord, bytes, bytearray]:
+        """
+        Serializes a list of tensor metadata and tensors emitted by ExecuTorch
+        into a binary blob.
+
+        Args:
+            tensor_buffer: A list of deduplicated tensor data.
+            tensor_map: A map from tensor name (fqn) to tensor index inside 'tensor_buffer'.
+            tensor_metadata: A map from tensor name (fqn) to tensor metadata.
+
+        Returns:
+            A binary blob that contains the serialized data.
+        """
+        raise NotImplementedError("serialize_data")
+
+    @abstractmethod
+    def deserialize_tensors(
+        self, blob: Union[Cord, bytes, bytearray]
+    ) -> Tuple[List[bytes], Dict[str, int], Dict[str, Tensor]]:
+        """
+        Deserializes a blob into a list of tensor metadata and tensors. Reverses the effect of serialize_tensors.
+
+        Args:
+            blob: A binary blob that contains the serialized data.
+
+        Returns:
+            A tuple of (tensor_buffer, tensor_map, tensor_metadata).
+        """
+        raise NotImplementedError("deserialize_data")