ENH: Allow users to replace found devices directly

[tangkong]

Expected Behavior

If we can find a device in a checkout, we should be able to swap it out / find-replace it smoothly.

In addition, we should update this table as we make edits to the file.

Current Behavior

Currently we find all the devices at FindTemplatePage load-time, and that list stays static.

Possible Solution

Wire the click-action in the devices/signals table to add a row with that device pre-loaded

Look for that device, determine its type, and prime a HappiSearchWidget to only return devices of a similar class

Re-populate this table after one of these replacements has happened, and optionally at reasonable intervals

Context

Comments from Ken and Zach in #198

Your Environment

pcds-5.7.3, atef v1.0.0