Dealer's Choice uses separate hand for game selection

[ctm]

Consider refactoring Dealer's Choice so that the game that is selected is done in the same hand as the game is played.

I added Dealer's Choice during the WSOP-Style series in 2023 and cut at least one corner to get it done "in time" (and even then it was late). Specifically, Mb2 currently treats game selection as a hand unto itself (i.e., getting its own hand number), rather than a preamble to the first hand of the new game. I think that's a poor choice, although I haven't really thought about it enough to be sure. There are currently no known bugs associated with how its implemented, but we also don't implement hand histories. When we do implement hand histories, if we don't refactor, the game choice will be a separate hand.

If I do choose to merte them, doing so is easy in principle, but shouldn't be done until we have a nice way to use the database to do regressive tests, since it would be trivial to introduce a subtle bug.