✨ Port all contracts to Foundry

[cairoeth]

• Ports all tests to foundry
• Updates READMEs to reference correct directory paths
• Updates client scripts to use correct foundry output paths
• Updates package.json to use forge and anvil instead of hardhat
• Formatted files using foundry's formatter (forge fmt)
• Moved contracts to src folder

Speed difference:

forge t  0.76s user 0.61s system 188% cpu 0.727 total

yarn test  20.70s user 0.70s system 222% cpu 9.612 total

Around 13x faster.