Fix log_config

[josejg]

Foundry's train and eval scripts use the log_config helper to log the parameter config. However, log_config breaks the logger abstraction by directly logging to wandb and/or mlflow.

This PR uses the logger.log_hyperparameter method which relies on the same method calls for wandb and mlflow. In addition this PR allows custom loggers to be able to log the config which is not currently supported.