Upgrade to firehose-core

[maoueh]

We have created https://github.com/streamingfast/firehose-core so that chain's integration only work is now to bump firehose-core dependency to benefit from all the new features Firehose & Substreams has to offer.

The firehose-core deals with everything (flags, config, set-up, all libraries, etc.). While there is no direct upgrade procedure, the steps are essentials to port https://github.com/streamingfast/firehose-acme/blob/master/cmd/fireacme/main.go to firehose-cosmos and fill up properly the firecore.Chain struct. After that it's a matter of then deleting what is not used.