Add a non-daq scan with a duration parameter (wait per_step)

[tangkong]

Expected Behavior

We should have a plan that allows scans to specify a dwell time per scan point.

Current Behavior

daq scans currently do this, but a way to do this without tying up the daq would be great

Possible Solution

Either:

• implement a per_step function that sleeps. This could be hard to parametrize, so could be annoying
• Take over tom's old PR that implements a delay-device (ENH: add a "busy" device bluesky/ophyd#1028)

Context

Some conversations with the xcs folks brought this to our attention

Your Environment

pcds-5.4.1