chore: use separate store paths for channels/creators

[DimitrisJim]

Description

the channels are now stored under channels/{channel-id} while creators under creators/{channel-id}. If someone has better path suggestions, feel free to mention em!

closes: #7631

---

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[sonarqubecloud]

Quality Gate passed for 'ibc-go'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[damiannolan]

lgtm