Evolve new RPC message type and handling

```[tasklist]
### Tasks
- [ ] RPC Param to take object rather than map and simplify code for deserialising to write praram names and type before calling relevant rpc handler
- [Done ] Review how the RPC registration & routing happens
```

Review how RPC registration and routing currently happen, then trace the existing RPC parameter deserialization and handler call path. The issue is done when RPC parameters are accepted as an object and parameter names and types are written before the relevant handler is called.

Written by the indexing model from the issue text.