retries: Make retry budgets default

Currently, the max_retries circuit breaker is set to a static value of 3 by default. Retry budgets 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.