Set up integration test environment with sequencer node

[0x-r4bbit]

Currently we're running our integration tests against V03State which is the state machine that LEZ uses to process transactions.
If I remember correctly, the reason we went this way is because it was easier to get integration tests up and running in our standalone repository, instead of trying to get the sequencer to work.

This issue is about revisiting this. We should be running our integration tests also against a local sequencer (ideally against dev/test networks as well, but that would be a follow-up step to work on).