To make this happen, restart idle in timeout handler (also start it
when user bonks Play button and stop it when they bonk Pause or Stop
button).
The idle also needs a lower prio than TaskPriority::Repaint,
otherwise the higher-prio events from our idle are going to starve UI
repaints in the scheduler queue

Change-Id: I4c767c3533e0e2ee9015c48b17075db5e0dc7ade
Reviewed-on: https://gerrit.libreoffice.org/70068
Tested-by: Jenkins
Reviewed-by: Katarina Behrens <Katarina.Behrens@cib.de>