[TASK] Cosmwasm vanchor relayer support

[dutterbutter]

Overview

We have support for the Substrate/EVM vanchor, but we need to integrate support for the cosmwasm vanchor as well.

Checklist

• [ ] Add a handler for the cosmwasm vanchor, using the other handlers as a reference.
• [ ] Add a test for it as an integration test.
• [ ] Add inline documentation to the file and wherever else is relevant if there's missing docs.