[orchagent] implement ring buffer feature with a flag

[a114j0y]

What I did

• fix the covariant return type issue of swss::TableBase* Consumer::getConsumerTable() const override
  • it should return swss::ConsumerTableBase *
• add a ring thread for orchdaemon
• support ring buffer feature

Why I did it

• increase the speed for APP_ROUTE_TABLE consumers doing tasks

How I verified it measure the performance with PerformanceTimer