[codemod][py3.12] Convert dataclasses mutable default values to use default_factory

Summary:
As of [Python 3.11](https://docs.python.org/3.11/whatsnew/3.11.html#dataclasses), dataclasses now only allow defaults that are hashable. Using mutable (non-hashable) default values under Python 3.11+ will cause a runtime error:

```
ValueError: mutable default <class 'problematic.ClassName'> for field <field> is not allowed: use default_factory
```

This codemod attempts to automatically convert mutable defaults to use `default_factory`

NOTE: The change is not semantically equivalent to before the change. Before, all dataclass instances with a mutable default value were sharing the same instance. This change results each dataclass instance using a new instance of the mutable value. It is likely that the before state was a latent bug, but it's still a behavior change!

Reviewed By: itamaro

Differential Revision: D72111785

fbshipit-source-id: fb6d3e1c7fab3f3d2452d6335233fec767551eef

Author: generatedunixname647790274085263

mmf/models/transformers/base.py

@@ -38,7 +38,7 @@ class BaseTransformerModalityConfig:
     # Encoder to be used to encode this particular modality
     # This is actually: Union[EncoderFactory.Config, Encoder.Config]
     # NOTE: Waiting on https://github.com/omry/omegaconf/issues/144
-    encoder: Any = IdentityEncoder.Config()
+    encoder: Any = field(default_factory=lambda: IdentityEncoder.Config())
     # when type is text, whether to consume raw text or intermediate representations
     # from frozen text encoder. This can be potentially also used by other modalities.
     consume_raw: bool = True