Name request log actions so they say what they mean (closes #229)

Rename too_large, rate_limited, rule_blocked and denied, and split banned
into temporarily_banned and permanently_banned by whether the ban runs out.
A request that makes a ban permanent gets permanently_banned. A ban the
request itself makes gets the value for that ban, and in observe mode
would_action names the ban enforce mode would have made.

The offence kind rule_blocked follows, as a metric label and a key in
clients.json.

Model: opus-5-5

internal/discriminator/denynets.go

@@ -19,7 +19,7 @@ func (denyNets) check(_ context.Context, rq *request, _ time.Time) *verdict {
 	for _, netblock := range rq.h.config.DenyNets {
 		if netblock.Contains(rq.client) {
 			return &verdict{
-				action:  requestlog.ActionDenied,
+				action:  requestlog.ActionClientDenied,
 				figures: map[string]any{figureNetblock: netblock.String()},
 			}
 		}