Autoplace: slurs intersect accidentals

This is deliberately allowed because while in cases like the one shown, the alternative is not so bad, that approach doesn't work for steeper slurs. See for instance #274208: Slur too high with accidental for an extreme case. Consulting various sources, it was decided that allowing the collision would be preferable. Other cases too where realistically there just isn't a good solution, like notes in other voices that don't allow for any easy placement of the slur - you end up with a slur that looks like it is connected to a different note than it actually is.

But we could probably be smarter, allowing the collision only if avoiding it would cause the slur to move too much. There is now code to make multiple passes like that for interior collisions, we could potentially take advantage of that approach for the endpoints as well.