lineup_and_center() plan could accept any movable

[prjemian]

The lineup_and_center() macro (in 50-controls.py) accepts a scaler channel, or EpicsSignal (any readable) and a motor. The code could/should be generalized to accept any movable Signal.

This plan would be a valuable to apstools.plans.

Also, it has code that, given some readable signal, identifies if it is from a ScalerCH object and that returns that object. While this is nice code that can be extracted to its own function, seems that the scaler should channels should already provide this information directly. (motivation: Sometimes, one wishes to modify the count time or other aspect of the scaler object when using a scaler channel as a detector.)

[prjemian]

That same pattern of a channel identifying its containing object should be applied in other multichannel device support such as EpicsScaler, usersCalcs, userCalcouts, ...

Usually, channel.parent points to some structure that is a below the containing object. In the case of ScalerCH, the channels are three levels below. That is, channel.parent.parent.parent is the ScalerCH object.

[prjemian]

Note (bluesky/bluesky#1267 (comment)): the kind="hinted" attribute is important.