mostly standardize to object event to prep for disassembly

include/event_data.h

@@ -46,7 +46,7 @@ bool32 CanResetRTC(void);
 u16 *GetVarPointer(u16 id);
 u16 VarGet(u16 id);
 bool8 VarSet(u16 id, u16 value);
-u8 VarGetFieldObjectGraphicsId(u8 id);
+u8 VarGetObjectEventGraphicsId(u8 id);
 u8 *GetFlagPointer(u16 id);
 u8 FlagSet(u16 id);
 u8 FlagClear(u16 id);