rename shop item locations in spoiler/enums to make sense

[briaguya-ai]

any numbering system will be ambiguous, it'd be better to have

BLARG_SHOP_LEFT_SIDE_TOP_LEFT
BLARG_SHOP_LEFT_SIDE_BOTTOM_LEFT
BLARG_SHOP_LEFT_SIDE_TOP_RIGHT
BLARG_SHOP_LEFT_SIDE_BOTTOM_RIGHT
BLARG_SHOP_RIGHT_SIDE_TOP_LEFT
BLARG_SHOP_RIGHT_SIDE_BOTTOM_LEFT
BLARG_SHOP_RIGHT_SIDE_TOP_RIGHT
BLARG_SHOP_RIGHT_SIDE_BOTTOM_RIGHT

or something like that if possible instead