Subtitle/Audio delay: New UI

Description

On TV, when the delay is huge (50s in this case), it's really long to set due to the 50 by 50 increment policy.

We should set a new UI allowing to set the events we want to sync:

• Character speaks -> 'sound' button click
• Subtitle appears -> 'subtitle' button clicks
• VLC calculates the correct delay to apply.

Maybe this UI should be in addition to the old old, for small delays.

Expected behavior

Screenshot / video