[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: D72541748

fbshipit-source-id: 32a57309ed267f52813d54bb647e4ca5f9c67c58

Author: generatedunixname647790274085263

mmf/models/mmf_transformer.py

@@ -54,8 +54,8 @@ class Config(BaseTransformer.Config):
         freeze_image_encoder: bool = False
         tie_weight_to_encoder: Optional[str] = None
         finetune_lr_multiplier: float = 1
-        backend: BaseTransformerBackendConfig = MMFTransformerBackendConfig(
-            type="huggingface"
+        backend: BaseTransformerBackendConfig = field(
+            default_factory=lambda: MMFTransformerBackendConfig(type="huggingface")
         )
         modalities: List[BaseTransformerModalityConfig] = field(
             default_factory=lambda: [