Document and Expose CanDynamax Flag

[sora10pls]

Setting that flag still doesn't let random Trainers Dynamax; probably has to do with the battle background not being suited for gigantic Pokémon. :(

Also now hide properly hide some stuff:

• LGPE: Hide all Dynamax-related controls and EVs.
• SWSH: Hide all Hidden Power-related controls and AVs.