Adds a dockerfile for the `gas-oracle` as well as adding it as
a service in the `docker-compose.yaml`. It is not enabled by
default due to memory issues in CI already happening occasionally
where the integration tests are oom killed.

The `gas-oracle` is configured with a key that owns the
`OVM_GasPriceOracle`.

This PR adds the `gas-oracle` to the Github Actions
workflow that is responsible for publishing the docker images.