Make paste a separate undo transaction from preceding edits (#52003)

When undoing a paste, it is really confusing when that actually also
removes what was type right before the paste if the paste happened fast
enough after.

Release Notes:

- Fixed undoing a paste sometimes also undoing edits right before the
paste
8cbcadf196Lukas Wirth committed on 3/30/2026, 7:17:02 AM· committed by GitHubparenta17a1c1
6 files changedLine totals unavailable