Migrating to Foundry as default development framework

[Pabl0cks]

Set Foundry as SE-2 default Ethereum development framework, leaving Hardhat as an option for users that use the CLI to get started with their SE-2 project.

Major point will be cleaning up stuff and keeping it clean and minimal.

We could also change the order of Hardhat, Foundry in docs, SE website and CLI to show Foundry first.

We can add #813 changes also as mentioned here (maybe in next iteration after Foundry is merged?): #812 (comment)