add "splatting" of logging of fc sizes to LitCNN (and MLP)

[charlesfrye]

the conv channel sizes are "splatted" in the config -- logged as conv.1.size -- this would be good to add to the models.

i think a callback would be good -- adding a trawl through the modules to the "magic" WandbCallback for example

[charlesfrye]

this is done for LitMLP, but not LitCNN