🛠️ [TASK] : Rename cat-data-service to Catalyst Data Gateway or cat-gateway for short.

[stevenj]

Summary

Rename in the code and the code structure.

Description

We will use the term cat-gateway instead of cat-data-service.
cat-gateway is the short term to describe Catalyst Data Gateway.

We describe it now as a Data Gateway, because overtime it will evolve to have functionality to attest and publish data on libp2p as an integral part of the initial hermes/athena deployment. So rather than being a strict Database API backend, it will incorporate traditional backend functions with non traditional p2p networking operations.