Implement a foundry based testing framework

[npasquie]

There is a shared feeling that the current hardhat testing framework is hard to use, unstable, and generally a mess.
While we want to keep it because having the TypeScript-based framework is important for compatibility and e2e testing purposes, a new Foundry-based testing framework is needed for iterative, quick feedback smart-contract side development.
I will implement test contracts mocking everything that is happening outside of the host chain in Inco using Foundry cheat codes, and provide a base to write Solidity tests for the cERC20 implementation and future confidential smart contracts.
Please use this issue to give feedback while I start working on it.

[vkpatva]

can you assign this to me! @npasquie