ENH: enable searching for PVs to add to Collections

[shilorigins]

@YektaY has a PyDM / PyQt widget that can search the EPICS environment for all discoverable PVs, and list these PVs for selection, along with a string filter.  We can use this widget for adding Parameters to Collections, in collection_builder_page.ui / collection_builder.py

[tangkong]

I'm crossing my fingers that it isn't overly reliant on pydm, or that at least we can pull the search utility out into a normal qt widget/routine