unbeamed cross-staff tuplets

[rettinghaus]

In some cases there are tuplets crossing staves without a beam. To deal with this, @bracket.place and @num.place should allow the same values as @beam.place, i.e. "mixed" is missing.

see Gould p. 320:

What for does tupletSpan need @beam.with? (Edit by @bwbohl: for discussion about the necessity of @beam.with please refer to https://github.com/music-encoding/music-encoding/discussions/1030 )