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

Devin Linrequested to merge
work/devinlin/notifications into master

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)

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

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