feat: make a monorepo with ssj

[ClementWalter]

Feature Request

Describe the Feature Request

We currently have 2 repositories, this one and one for Kakarot in Cairo. In this repository though, we have

• some cairo contracts
• all the scripts to compile and deploy both cairozero and cairo
• all the end to end tests

So goal is to migrate all ssj into this repo and make it a monorepo.

The CI should run only the relevant tests depending on the changed files.