`HttpServer` and `WsServer` resources should be configurable at service level

[tgmichel]

SpawnTasksParams should include additional fields that can be used when calling the start_rpc_servers function to override:

• The default value for the number of threads in the HttpServer pool (currently hardcoded to 4).
• WS_MAX_CONNECTIONS, ideally one should be able to override this as well (currently 100).

[tgmichel]

• ws max connections is already customizable.
• In rpc-http-threads cli arg #8890 just took the same approach for the RPC HTTP thread pool size.