[OZ: M-04] Math library is vulnerable to shadow overflow

[ggviana]

The AuxMath library is a custom auxiliary math library that performs multiplication and division with rounding specifications.

The implementation of mulDivUp and mulDivDown first compute the multiplication of a uint256 with a uint256 without taking into account the possibility of an overflow in the product. The product could overflow into a uint512 in the multiplication step even if the result were to fit into a uint256 after the subsequent division. Hence the current implementation will not give the right result in such a case.

Consider using OpenZeppelin's Math library which implements the mulDiv function that is developed especially considering these scenarios and is widely accepted in the ecosystem.

[ggviana]

Fixed @ 89869ad

Implemented OpenZeppelin's ERC4626, which takes into account multiplication overflow