Remove MoneyPHP, use `float`s instead
This PR removes the moneyphp/money dependency and switches uses of Money to floats, like Magento already uses. Somewhere in the conversion from float to Money, precision is lost, resulting in a $0.01 difference between CBS and Magento.
Project version is bumped to 8.0.0 because this is a significant, backwards-incompatible change.
There are a lot of changes here, but they're all very straight forward.
Please review: @ahoffmann @weizhong-wang @lloyd-carter @KJOYNER