Implement a generic counter token bucket
We have the
_raw_t interface and a
_rw_t specialized one. Many use cases only need a single counter like for instance the circuit creation DoS defense would use that. Or #15516 (moved) introduce2 rate limiting.
After a discussion with nickm, it would be wise if we can simply implement a generic counter token bucket:
... with a single bucket in it and thus could generically be used by many subsystems.