Describe the new feature or enhancement

Raw.plot() currently does not accept a picks= argument, even though Evoked.plot() and Epochs.plot() do.
For a mostly-unified API it would be nice to add this parameter.

Describe your proposed implementation

This would be added as an argument to Raw.plot().
I suppose it can come after the n_channels argument. Ideally it would be the same for all classes, but that would break backward compatibility.

The behaviour and implementation should be similar to or identical to how it's done in Epochs.plot() and Evoked.plot().

Describe possible alternatives

Alternatively, the entire function call could be rewritten to match Evoked and Epochs. The would be nicer for the future, but it would break a lot of things in the short term, for a relatively minor improvement.

Additional context

Discussed on the MNE forum here: Unexpected behaviour Raw.pick