tick-n probes

Like profile-n probes, tick-n probes fire every fixed interval at high interrupt level. However, unlike profile-n probes, which fire on every CPU, tick-n probes fire on only one CPU per interval. The actual CPU may change over time. As with profile-n probes, n defaults to rate-per-second but may also have an optional time suffix. tick-n probes have several uses, such as providing some periodic output or taking a periodic action.