[MainUI] Allow the user to copy and paste the Thing ID and Channel IDs more easily

[rkoshak]

More discussion on this is located at https://community.openhab.org/t/openhab-3-0-my-getting-started-and-notes/106467.

One thing PaperUI got right was that nice little button to copy the Channel ID to the clipboard. As I migrate my Items and Things to OH 3 I find myself choosing better names for some of my Things and as a consequence the Channel IDs changed. I would paste the Items into the "add Item from text config" and edit the Channel there. But in another browser tab I'd have to navigate to the thing, then the Channel, then open the Channel config before I could get to a place where I could copy even a part of the ID. Even if the Thing ID were made selectable from the list of Things this workflow would be greatly improved. When I try to select the text though it won't let me (latest Firefox is the browser).

This is a usability related feature request.