Print param groups after initialization

[ottonemo]

We should be verbose about the param groups that are added after initialization (since we support wildcards and it may be intransparent which param groups are created from that).

For example:

>>> net = Net(optimizer__param_groups=[('dense*', {'lr': 0.03})])
Initializing module!
Setting param group {'lr': 0.03} for dense0.weight, dense0.bias, dense1.weight, dense1.bias.

[thomasjpfan]

I can see two ways to implement this feature:

1. Use a callback with a sink parameter that prints the param group during on_train_begin.
2. Print the param group in NeutralNet.initialize_optimizer when verbose is truthy.

What do you think?

[benjamin-work]

@ottonemo do you have an opinion on that?

[ottonemo]

Since the introduction of virtual parameters we have dedicated setter methods for these parameters. This means that we have two places where this message may be relevant:

1. during initialization from Net kwargs
2. when setting using set_params(optimizer__0__lr=0.03) There should probably a utility function to print this message (of course we could think about a special callback that gets triggered when parameters are set but I don't think this is particularly helpful).