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/metrics_test.go

@@ -125,15 +125,15 @@ func TestMetricsCountLimitsAndBans(t *testing.T) {
 	})
 
 	// SWW_BAN_RESPONSE=close sends no status at all.
-	s.get(denied, 0, requestlog.ActionDenied)
+	s.get(denied, 0, requestlog.ActionClientDenied)
 
 	// A first broken limit bans for an hour.
 	s.get(client, http.StatusOK, requestlog.ActionForward)
-	s.get(client, 0, requestlog.ActionRateLimited)
+	s.get(client, 0, requestlog.ActionClientIsRateLimited)
 
 	metrics := s.scrape()
 	wantMetric(t, metrics,
-		`sww_requests_total{action="denied",instance="app",status_class="none"}`, 1)
+		`sww_requests_total{action="client_denied",instance="app",status_class="none"}`, 1)
 	wantMetric(t, metrics, `sww_rate_limit_hits_total{instance="app",`+
 		`kind="requests",window="minute"}`, 1)
 	wantMetric(t, metrics, `sww_offences_total{instance="app",kind="limit"}`, 1)
@@ -147,7 +147,7 @@ func TestMetricsCountLimitsAndBans(t *testing.T) {
 	// A limit broken again right after would ban for three hours, longer
 	// than SWW_MAX_BAN_DURATION, so the ban is permanent.
 	s.get(client, http.StatusOK, requestlog.ActionForward)
-	s.get(client, 0, requestlog.ActionRateLimited)
+	s.get(client, 0, requestlog.ActionClientIsRateLimited)
 
 	metrics = s.scrape()
 	wantMetric(t, metrics, `sww_rate_limit_hits_total{instance="app",`+