Review flip for attachments

- [x] Flipping an attachment can generate (unexpected) problems in other frames (if the attachment is used more than one time), probably in this case we should offer the possibility to automatically duplicate the attachment and flip it
- [x] Make the flip work for multiple tiles (with no canvas selection) when the timeline range is used.
- [ ] Check cases where the same attachment is flipped even when the canvas selection is used (because this can bring a lot of visual issues/confusion in the final result)