More Blender VSE stuff for 4.2

I did a bunch of work for Blender 4.1 video sequence editor, and since no one revoked my commit access, I continued in the same area for Blender 4.2. Are you one of the approximately seven Blender VSE users? Read on then!
Blender 4.2 has just shipped, and everything related to Video Sequence Editor is listed on this page. Probably half of that is my fault work, and since 4.2 is a long term support (LTS) release, this means I’ll have to fix any bugs or issues about that for three more years, yay :)