Customize retry config for CamundaRestClient

Currently the CamundaRestClient [hardcodes GotRetryConfig](https://github.com/camunda/camunda-8-js-sdk/blob/5a61668880dcc70f90d86b4891bc7f933d886f9b/src/c8/lib/CamundaRestClient.ts#L175), so that it can only be used with the defaults. I would like to be able to customize the configuration, because I have use cases where backpressure gets very high.