feat: package revamp part 2 (setup)

I split the package revamp into three separate PRs for easier reviews.

Descriptions

part 1 (cleanup): removes all contracts, configs, dependencies
part 2 (setup) adds:
- an automated script (fetch_contracts) that fetches, preprocesses, restructures and commits the contracts from a given branch/tag/commit of era-contracts
- update-contracts workflow: runs the script to update the contracts and creates a pull request
- config files for both hardhat and foundry
- OZ v4 dependencies with aliases (package.json, remappings.txt)
- basic CI: compiles L1, L2 and SC contracts separately with both hardhat and foundry
- readme with installation and usage sections
- populated package.json
- publish-package workflow
part 3 (contracts): adds all the contracts from the dev branch of era-contracts (auto generated commit: execution result of the above mentioned automated script) - will not be merged, the update-contracts workflow will be used instead