Display the message in WorkDoneProgressEnd

[hokein]

Looks like the message in WorkDoneProgressEnd is ignored by the client (at least VSCode),

It would be nice to display this message in some sort of form.

[dbaeumer]

The interesting question is where to present it since the notification showing the progress closes on done :-). Need to think about something.

[dbaeumer]

I still don't have API for this in VS Code. So not much I can do.