Handle RPC tests for runtime calls

## Task summary
We have implemented runtime calls through RPC in this #3228 . This was added to test the `ParachainHost` runtime exports.
Since this exposes all the runtime calls, we need to add test coverage to it.

Few open questions
- Do we need to cover all the runtime calls?
- Should we write all the tests in zombienet or cover it in the Go tests as well?
- How to prioritise the tests?

## Other information and links
- Task to implement zombienet tests #3229
- PR that implements `state_call` RPC #3228