yanshenxian

[enhancement request] make retryer and sleeper more flexible

5

## sdk version: 4.0.0 ``` B2StorageClient client = B2StorageClientFactory .createDefaultFactory() .create(APP_KEY_ID, APP_KEY, USER_AGENT); ``` The default `B2RetryPolicy` wil try max 8 attempts and each time wil sleep at least 1...