Reduce complexity of sequencer transform code by removing recursivity. This is possible by treating meta strips (mostly) as any other strip and containing all transform code within SEQ_ functions. Unfortunately internally meta strips still require special treatment, but all complexity from code all over transform code seems to be possible to contain within one function. Functional change: Previously adjusting handle of single image strip moved animation. Now animation is not moved, which is behavior for all other strips. Reviewed By: sergey, mano-wii Differential Revision: https://developer.blender.org/D11493