Removing a peer's routes, sweeping its stale ones and sweeping the
attribute sets were each written out as their own spawn_blocking, and
each dealt with a failed task differently: the periodic sweep dropped a
panic on the floor, and a restarting peer whose kept routes could not be
removed was logged as "removed 0 routes". off_thread does it once, and
every caller logs a failure.
Also:
- the hard-reset wrapping of a NOTIFICATION is one function in the FSM;
- the two ways to close every session are one, and the registry has one
leave() rather than leave() and shutdown();
- the dialer says why a session ended with SessionEnd::reason, and no
longer turns a result into a result;
- as_path_prepend is parsed in one place, and the limits in error texts
come from the constants rather than being written out;
- router_id and cluster_id are parsed by one function;
- the exporter builds its Egress in one place;
- the fields a session keeps only to hand to its handle are fewer:
route_refresh is a bool, not a copy of the families;
- counting the stale routes removed cannot underflow;
- docs that had gone stale: the proto still said there was no route
reflection, the advertiser's module doc said it announced only our own
routes, from_server listed two of its five sources, and so on.
Tests for what had none: which session ends count as restarts, the Hard
Reset wrapping, the graceful restart settings, the dialer's jitter,
withdrawals in MP_UNREACH_NLRI, and AS_TRANS on a two-octet session.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
