[Forchheimer] Does this work for multi-phase flow?

In !2414 (merged), @martins and I discussed if Forchheimer (or our implementation of it) works for multi-phase settings. It is permitted in the code and, but some variables have names that suggest one-phase flow regimes. Moreover, there is this comment:

// This is important in the case of a one-phase region in two-phase flow. The non-existing
// phase has a velocity of zero (kr=0).

see line 472 in https://git.iws.uni-stuttgart.de/dumux-repositories/dumux/-/blob/59ee4e5e26d6646dcf7670df8b4f7193a6fe3fda/dumux/flux/cctpfa/forchheimerslaw.hh