refactor: use callbacks

[richard-ramos]

To avoid having to call a function to free allocs, go-waku and nwaku are now using callbacks. This PR updates the code to match the new API

• [x] use callbacks for API functions
• [x] remove jsonResponse
• [x] handle deserialization for functions that return json, strings and ints(and booleans)
• [x] ensure tests work