Improve state migration tool (`celo-migrate`)

```[tasklist]
### Tasks
- [ ] https://github.com/celo-org/optimism/issues/135
- [ ] https://github.com/celo-org/optimism/issues/143
- [ ] https://github.com/celo-org/optimism/issues/142
- [x] Disable OP governance for L2 OP deployment
- [x] Run `DeployConfig.Check` earlier to provide better errors
```
