Make sure we provide icon and contextualTitle properties for the test explorer

[luabud]

From VS Code's update 1.46:

https://code.visualstudio.com/updates/v1_46#_flexible-layout

For extension authors contributing views or view containers

When views are moved around the workbench, they sometimes need to be presented differently, either with an icon or extra context if they aren't in their default location. When contributing a view, authors may now provide an icon property and a contextualTitle. If not provided, these will default to the icon and title of the view container to which they are contributed.

We should check if we do it for test explorer, if not we should do it :)

[karthiknadig]

Closing this as stale