Provide "restart required" dialog on Windows, too

[fmoc]

This commit provides a remodeled version of the "Update finished" dialog implemented in #11201.

Fixes #10980.

[TheOneRing]

As far as I can remember, the current message also allowed a user to decline an update.
So we need Skip update, Restart and update, Update later

[TheOneRing]

Also please add a changelog entry

[fmoc]

As far as I can remember, the current message also allowed a user to decline an update.
So we need Skip update, Restart and update, Update later

There are a "no URL dialog" and an error dialog in the NSIS updater class that offers these options but isn't regularly shown apparently. This dialog is shown when the update has been downloaded sucessfully already.

We need to think about consolidating all these (partially redundant) dialogs. However, this is outside of this PR's scope, which replaces a specific systray message with a dialog.

[TheOneRing]

your right