Retry HttpDispatch & ThrottlingException errors

[DarrenTsung]

💡 Feature description

Hi, thanks for the great library! We've seen spurious HttpDispatch errors (connection reset, DNS lookup failures) in production and it'd be nice if the Dynomite retry policy handled this for us in addition to the DynamoDB errors.

💻 Basic example

I've made this change in a fork: figma@70db2e0.

[DarrenTsung]

I also noticed that while Dynomite's retry policy will retry errors like TransactWriteItemsError::ProvisionedThroughputExceeded, it doesn't retry throttling errors which appear to be classified as RusotoError::Unknown(_).

The response body for the http request looks like:

{\"__type\":\"com.amazon.coral.availability#ThrottlingException\",\"message\":\"Throughput
exceeds the current capacity of your table or index. DynamoDB is
automatically scaling your table or index so please try again shortly.
If exceptions persist, check if you have a hot key:
https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/bp-partition-key-design.html\"}"

I've updated the fork with a fix for this as well:
figma@3eb298e