widgets/notifications: Cleanup, fix some visual issues, and add jobs

Note: There was a lot of whitespace that my IDE is now removing.

Fixes job notifications not being dismissable (#208 (closed)), and imports an implementation from workspace for the progress bar and actions.

Fixes notification contents not being clipped when being dragged (teams/plasma-mobile/issues#287 (closed))

Also fixes notification text being spread over multiple lines unnecessarily (teams/plasma-mobile/issues#302 (closed)).