Add ability to manage public_debug namespace

[SozinM]

Summary

Public debug namespace (rpc_call hmy_setLogVerbosity) is not manageable via cmd options or config file.

Current Design

Not manageable

Problems

We host a shared RPC node and don't want to allow users to affect the node state in any way.

Proposal

Make public debug namespace manageable alongside with private debug namespace using:

[RPCOpt]
  DebugEnabled = false