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.

This commit adds the `gas-oracle` which is an offchain entity
that sends transactions to L2 to update the gas price. It must
be configured with a private key as the `OVM_GasPriceOracle`
is owned.

The `gas-oracle` is added to the changesets setup.

Tests are included as well as CI. Dockerizing will happen
in a follow up PR.

The `gasprices` package implements the logic that updates
L2 gasprices on the Optimistic Ethereum Network.
Co-authored-by: Karl Floersch <karl@karlfloersch.com>

fix: skip codechecks for PRs from external repos

and fix a solidity linting error

compliant with the standard bridge