chore: increase timeouts for childchain healthchecks

[ayrat555]

Overview

On the latest master I can't start reorg docker-compose locally, because it fails with the childchain is not healthy error:

Creating elixir-omg_postgres_1 ... done
Creating elixir-omg_geth_1     ... done
Creating geth-1                ... done
Creating geth-2                ... done
Creating nginx                 ... done
Creating childchain            ... done

ERROR: for watcher  Container "d7e5a929f9d7" is unhealthy.

ERROR: for watcher_info  Container "d7e5a929f9d7" is unhealthy.

I increased timeouts for childchain healthchecks. After that docker-compose starts without issues.

Changes

Describe your changes and implementation choices. More details make PRs easier to review.

• Increase the timeouts for childchain healthchecks
• Use localhost in healthchecks
• Add reorg tests to the README