Diet Unlock System

[StarbotArc]

This PR is intended to bring #SELECTABLE back to use by turning it into a visibility toggle instead, or an unlock system in other words.

With this pull request, it modifies:

• Function GetSteps() to filter out unselectable songs that have not been cleared - SongUtil.cpp
• Adds getters and setters for m_SelectionDisplay - Song.cpp and Song.h
• Turns SelectionDisplay into a global enum - Song.h, NotesLoaderSM.cpp, NotesLoaderSMA.cpp, NotesLoaderSSC.cpp, NotesWriterSM.cpp, NotesWriterSSC.cpp, NotesWriterETT.cpp, SongCacheIndex.cpp, GameConstantsAndTypes.h, and GameConstantsAndTypes.cpp (yes it's that big)
• Adds Lua hooks such as IsSelectable() and SetSelectable() - Song.cpp
• Function WHEELDATA.SetAllSongs() to do the same thing as GetSteps() in SongUtil.cpp, but specifically for Rebirth - 10 WheelDataManager.lua

BONUS:

• Adding AddChild Lua function, why not? - ActorFrame.cpp

This PR isn't exactly done yet, as it needs a form of saving state at some point, with maybe fancier features.

This PR is ready to be reviewed and pulled, this honestly is anticlimactic after literally posting yesterday.