Improve PyTorchFileRecorder enum deserializer error message

[laggui]

Trying to import a pytorch model into its corresponding Burn implementation can be a little difficult for new users, especially if the definition involves multiple enum modules to match the pytorch structure.

If the definition is not exact on the first attempt, which usually involves remapping some keys, it usually leads to an error like:

Failed to load model: DeserializeError("Serde error: failed to deserialize: No variant match for LayerTypeRecordItem")

This is not very helpful. We should try to provide a more helpful error message.

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