Test internal/private variables in contracts

[Mokita-J]

When testing the attacks it is good to have access to values of internal or private variables of the vulnerable contracts because it allows us to access wether the vulnerability was exploited or not.

Currently hardhat does not allow that: NomicFoundation/hardhat#2645

[Mokita-J]

hardhat-exposed automatically exposes internal functions.
However, it is not useful for internal/private variables and it supports solidity version >= 0.6.0.

[Mokita-J]

use ethers.provider.getStorage(address, slot) for reading private variables from a contract