04efca91f9
When slipping meta strip, effect position was not updated. These updates are limited to VSE core code, so function `SEQ_time_slip_strip()` was added to resolve this issue. This also simplifies operator code, so it does not have to deal with recursion and doesn't need to hold quite detailed strip state for when operator is cancelled. Pull Request: https://projects.blender.org/blender/blender/pulls/113200