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/history_test.go

@@ -31,9 +31,9 @@ func TestHistoryKeepsEachRequestOfTheClient(t *testing.T) {
 	s.get(fromDE, http.StatusOK, requestlog.ActionForward)
 	clk.advance(time.Second)
 	s.get(fromDE, http.StatusOK, requestlog.ActionForward)
-	s.get(fromDE, http.StatusForbidden, requestlog.ActionRateLimited)
+	s.get(fromDE, http.StatusForbidden, requestlog.ActionClientIsRateLimited)
 	clk.advance(time.Second)
-	s.get(fromDE, http.StatusForbidden, requestlog.ActionBanned)
+	s.get(fromDE, http.StatusForbidden, requestlog.ActionTemporarilyBanned)
 
 	want := ratelimit.History{
 		FirstSeen: start,