Provide the ability to filter regions in a plex

[Joe-Winchester]

In a CICS Plex all of the regions are shown as tree items.
For a large plex or a plex where the user only works with a set of preferred regions, allow the ability for them to filter the list of regions shown.
This could be similar to how programs/files and other resources are filtered.
When this is done users will be able to set their filter of preferred regions and then work on those only