SC2: Generator for raceswap mission variants

[EnvyDragon]

What is this fixing or adding?

Adding functionality to shuffle in race-swapped map variants if user opts in; that is, if a yaml has Wings of Liberty missions enabled but Terran missions disabled, they can still get (for example) the Zerg and Protoss versions of Smash and Grab shuffled into their mission order.

Currently the only options are disabled and shuffle_all; eventually I plan to add an option that will randomly pick just one of the available variants, but that will require some extra work.

Mission variants added here:

• The Outlaws (Z and P)
• Zero Hour (Z and P)
• Smash and Grab (Z and P)

How was this tested?

Maps were tested by playing them a few times to ensure they were beatable; generation was tested by generating a bunch of mission orders with the maps either enabled or disabled to ensure behavior was as expected

[EnvyDragon]

Draft PR because vanilla and vanilla_shuffled mission orders are consistently failing to generate, even if swaps are disabled (ie. nothing should be different)

EDIT: Fixed!