Implement adaptive rate limits

[jonsyu1]

What happened?

Sending requests to an overloaded server retries up to the configured limit and then gives up.

What did you want to happen?

Limit the number of concurrent outbound requests to the server based on previous responses from the server. When the limit has been reached, wait until outstanding requests finish before sending new requests.

The conjure-java client switched to adaptive limits to cooperate with the server to send requests at a reasonable rate. Can we implement an AIMD limit for this client?