This is a smaller rewrite/refactor of the VSE copy paste code to use the file copy buffer logic that is used in other places of Blender.
This makes Blender able to copy paste between Blender processes.
It can also paste successfully after closing and reopening Blender.
Other than that, the functionally should remain the exact same as the current copy paste operator with one exception: Scene strips does not retain their scene pointer when pasting into the same file.
This is to make it consistent with how it was before when copy pasting between .blend files.
(The scene data for the scene strips were never copied in when doing that)
Logic for pulling in or linking scenes into new or current files are purposely left for later when a proper proposal of how this would work in a nice fashion is done.
Now the strip data gets copied either fully or partially besides for scene strips. There only the script data gets copied and not the scene data.
If there is a audio/video data block of the same name as in the paste data, it will be reused to reduce potential duplication of data.
Pull Request: https://projects.blender.org/blender/blender/pulls/114703
e7f0bb24f7