retries: Make retry budgets default

Currently, the `max_retries` circuit breaker is set to a static value of 3 by default. [Retry budgets](https://www.envoyproxy.io/docs/envoy/latest/api-v2/api/v2/cluster/circuit_breaker.proto#envoy-api-msg-cluster-circuitbreakers-thresholds-retrybudget) enable a better way to protect against retry storms that scales with the number of active requests.

One may have the same behavior as the static `max_retries` circuit breaker using retry budgets by setting the percentage to 0% and a minimum retry concurrency of the desired static value, so it might also be worth discussing whether the `max_retries` circuit breaker could be deprecated.