Create `celestia` DA implementation

[tzdybal]

Celestia specific DA implementation should use celestia-node HTTP API. This way https://github.com/celestiaorg/dalc/ is not needed anymore.

Related:

• service/rpc: Add a separate rpc service to handle all exposed endpoints celestiaorg/celestia-node#693
• chore: adapt node cmd to app/cosmos celestiaorg/celestia-node#755
• feat(service/rpc): add /namespaced_data endpoint celestiaorg/celestia-node#745