Allow user to refresh or replace a data source

[padraic-shafer]

Currently this happens only when the "bluesky cloud" button is clicked.

We either need to enable functionality via the QTiledWidget panel, or extract that functionality into a modal dialog (akin to a File Open browser).

PyMCA expects sources to be selected before the panel Widget is open/active. Using a separate dialog would also free up space for displaying richer info on the panel widget. However, if search is frequently used, this would be better to have in a defined area on the panel.

With the limited screen space available, we could consider using collapsible sections for:

• Search
• Results (catalogs, run Ids, streams)
• Data channels