Original commit from Christoph only modification is to remove selected only check as you can't select annotations so they don't show up with the option on
The issue was that with the move to Grease Pencil v3,
annotations and normal GP use different IDs and support to show annotations
wasn't added back in.
This makes it so annotation keys are shown if "Only Show Selected" is disabled,
which works in the Dope Sheet and in the timeline.
In order to not show annotations of the scene twice, the scene-specific code is removed.
The annotations are now shown in a more generic way.
Pull Request: https://projects.blender.org/blender/blender/pulls/134565
codywinch
d8f619f468