Feature request: Adding lam to the regularizer class

[pkassraie]

https://github.com/ott-jax/ott/blob/ea7d5b9c162146fa8e716f24fad28b89b34712d8/src/ott/geometry/regularizers.py#L35C1-L35C33

Since all regularizer functions accessible to the user have a property $\lambda$ which controls the regularization strength, would it not make sense to add it to the abstract class? Sometimes in the code it make sense to do cost_fn.regularizer.lam but this gives a warning in the interpreter, as it thinks not all regularizers have a property lam.