feat: package revamp

[benceharomi]

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