Run all the Solidity tests with Foundry

[RiccardoBiosas]

Context
At the moment the protocol code-base includes two types of Solidity tests: truffle-based Solidity tests and Foundry Solidity tests.. The truffle-based Solidity tests are run as part of the unit tests via the runSolidityTest helper.
I propose to convert them to Foundry tests to enforce more consistency in the code-base and because Foundry is the clear winner in terms of performance and testing capabilities.

TODO

• Move the Solidity tests to the Foundry directory
• Make the necessary refactoring to run them as tests with Foundry/forge - i.e.: replacing the before, beforeEach hooks with setUp. I'm estimating the refactoring process should be fairly straightforward
• Remove the runSolidityTest helper