Add support for exponential backoff in FirehoseProducer

[bobtiernay-okta]

Currently, FirehoseProducer performs linear backoff via:

//Full Jitter: https://aws.amazon.com/blogs/architecture/exponential-backoff-and-jitter/
long timeToSleep = RandomUtils.nextLong(0, Math.min(configuration.getMaxBackOffInMillis(), (configuration.getBaseBackOffInMillis() * 2 * attempts)));

While the code comment points to https://aws.amazon.com/blogs/architecture/exponential-backoff-and-jitter/, it fails to implement exponentiation:

Compare this with this code from FullJitterBackoff's calculateFullJitterBackoff:

public long calculateFullJitterBackoff(long baseMillis, long maxMillis, double power, int attempt) {
   long exponentialBackoff = (long) Math.min(maxMillis, baseMillis * Math.pow(power, attempt));
   return (long) (seed.nextDouble() * exponentialBackoff);
}

[GS-KeithLee]

Thank you for reporting the issue. We will plan this into our upcoming releases.