Fix T60194: Sequencer cut loses animation data for the right strip. Fixing the first also fixes the second. First attempt was delaying uniquename check at a later step of cut process, after everything had been duplicated. While this fixed first issue, second one became even more proeminent (it become active for all strips, and not only video/audio movie strips in meta's). So instead, passing along the list of (new) sequences, so that duplicated seqs can be put there immediately, before checking for unique names, henceforth ensuring even strips inside meta's get properly handled.