WidgetExplorer: improve screen reader accessibility
Widget Explorer contains a lot of information about widgets and plenty of buttons, but screen reader use is rather inconsistent - much of that is not read out, including the central aspects of the explorer: widget names and descriptions.
This change makes the components from the visual interface accessible to screen readers. Along the way, the text for uninstalling widgets was adjusted a bit to make it clearer and more consistent, using "uninstall" thoughout and leaving "remove" for the action that removes active widgets from panels/desktop without uninstalling them.
This should resolve teams/accessibility/collaboration#26 (closed)
I did not edit the Tooltip.qml file because I could not figure out where it is actually used to test out any changes. It has not seen any development except porting to new API in the last decade; if it's actually unused it may be worth deleting so that there's no more effort spent on porting it.