ClusterEntrypoint provides wrong executor to HaServices

The ClusterEntrypoint provides the executor of the common RpcService to the HighAvailabilityServices which uses the executor to run io operations. In I/O heavy cases, this can block all RpcService threads and make the RpcEndpoints running in the respective RpcService unresponsive.

I suggest to introduce a dedicated I/O executor which is used for io heavy operations.