…2497)

All commands that fail with the "Retryable" error label will be retried up to 3 times.
When the error includes the "SystemOverloaded" error label we apply exponential
backoff with jitter before attempting a retry.

Add adaptive token bucket based retry policy.
Successfully completed commands deposit 0.1 token.
Failed retry attempts consume 1 token.
A retry is only permitted if there is an available token.
Token bucket starts full with the maximum 1000 tokens.