Story (Required)

• For more info check https://github.com/argoproj-labs/argocd-agent/issues/171

Background and Approach (Required)

• A switch should be there to enable/disable the feature.
• A variable should be there to configure the interval.
• After provided interval agent needs to send a Ping event to principal. This event will be an dummy event with no data and it can be sent via a goroutine in /agent/connection.go/
  sender() function.
• Principal will receive this dummy event in principal/apis/eventstream/eventstream.go/recvFunc(), since it is a dummy event there is no need to process it and principal can send acknowledgement to agent and remove it from the queue.