[Notifications] Still compress "immediate" show, and delay individually
This ensures that the first
update() call with the summary will be shown
atomically to the user rather than show an empty job popup briefly.
Also handle the delay on a per-job basis, previously there was a common timer, which made no sense.
- starting a download in browser no longer has it briefly show no title after port to kuiserverv2jobtracker
- verified that an "immediate" job failing in the short window between request and show still shows up to the user to keep existing behavior where error result of an "immediate" job was always presented to the user