[BUG] Reconnection logic and Backoff policy doesn't work correctly

[RobertIndie]

I found that there are some issues with the BackoffPolicy:

1. We should use a new backoff instance for each use: https://github.com/apache/pulsar-client-go/blob/35ae05157b702804037446e1190a8f4e7557fdbf/pulsar/consumer_partition.go#L1656
2. In the reconnection logic, the checking for IsMaxBackoffReached doesn't respect the pc.options.backoffPolicy. https://github.com/apache/pulsar-client-go/blob/35ae05157b702804037446e1190a8f4e7557fdbf/pulsar/consumer_partition.go#L1700 Actually, the IsMaxBackoffReached is incorrect. We should respect the operation timeout and check the whole retired time instead of the backoff delay time.
3. From the view of API design, we should move the BackoffPolicy out of the internal package.

[crossoverJie]

@RobertIndie Is there any progress on this issue? Maybe I can handle it.

[RobertIndie]

Sure. Thanks. I assigned this to you.