Add transmission state manager with exponential back off

[vishweshbankwar]

This is the first PR towards refactoring the current mechanism for saving telemetry to storage and transmitting it back. The current implementation does not consider backing off exponentially in case of consecutive errors.

The current PR is adding TransmissionStateManager which will be used by the transmitter to decide whether it is ok to transmit to ingestion or directly save telemetry to storage. The usage will look like below.

if (_transmissionStateManager.State == TransmissionState.Closed)
{
    // Transmit telemetry to ingestion
    //  if the response code from ingestion falls under one of the retryable errors
    //  then save telemetry offline and call EnableBackOff to set the back off time for all transmissions
      _transmissionStateManager.EnableBackOff(response);
   
   // else for success code
       _transmissionStateManager.ResetConsecutiveErrors();
        _transmissionStateManager.CloseTransmission();
 

}
else
{
    // Save telemetry offline
}

The implementation is based on CircuitBreaker pattern with some modifications

[azure-sdk]

API change check

API changes are not detected in this pull request.

[TimothyMothra]

I would have more confidence if we had some unit tests for this.

[vishweshbankwar]

Need to look in to an issue with consecutive errors. Will re-open after fixing that.

[rajkumar-rangaraj]

LGTM