Fix tracking context warnings

[mwartell]

We get piles of

2023-12-19 13:39:19 2m37s WARNING  charmory.track:_wrapper:177 Parameters with prefix PyTorchClassifier have already been logged and will be overwritten. Use a unique prefix or start a new tracking context with `tracking_context` to avoid this warning.

warnings. Find what that complaint means and fix it.

[treubig26]

This is happening because when track_init_params gets used multiple times for the same class, the class's __init__ method gets wrapped multiple times, resulting in this warning. track_init_params should detect that the class has already been instrumented, and not re-wrap the __init__ method.