[Feature]: Move Nix tests into evmOS repo and migrate Solidity tests to Nix #50
Description
Summary
The nix tests from the Evmos repository should be moved to the evmOS repo.
When doing this, we should also remove the existing Solidity tests setup because it's flaky and hard to debug because of the legacy implementation and just do all of the E2E tests in Nix.
Issue Definition
Currently we have additional complexity in maintaining all test setups like the existing upgrade tests with Docker, integration tests with Solidity and yarn as well as the Python tests in Nix.
Proposed Feature
Move nix tests to evmOS repo and migrate current tests in tests/solidity to Nix setup.