Blender Git Loki

Fix T64995: box and circle select summary in Grease Pencil dopesheet.

The issue is that generic ANIM_animchannel_keyframes_loop can't
handle non-FCurve keyframes, so every selection operator does
its own looping over special key types, and the box and region
select operators didn't have code to deal with the summary.

This adds code to handle that in a similar way to other ops.