Name log fields, metrics and the Core Rule Set package for what they are (closes #192)

The first half of the naming audit: names now say what they are. `internal/waf` is `internal/coreruleset`. Log fields, the action `blocked_by_core_rule_set`, the metric and the alert event say Core Rule Set. Timings end `_ms`. Percentages say of what, as `rate_limit_percent` and `bytes_limit_percent`. Setting names follow in #234.

Judgement call: `blocked_by_core_rule_set`, not the audit's `core_rule_set_blocked`, to match `blocked_by_block_rule`.
Trips a reader: an existing state file holding `waf_blocked` or the anomaly scope `watch` stops the start and must be removed. `SWW_ALERT_EVENTS` listing `waf_block` must list `core_rule_set_match`.

Model: opus-5-5

internal/discriminator/refusallimit_test.go

@@ -107,9 +107,9 @@ func TestErrorBurstBreaksAtOneOverTheThreshold(t *testing.T) {
 			// The fourth is answered as the others were, breaks the error
 			// burst, and bans the client.
 			line := tc.refusals[3].send(s, client)
-			if line.LimitHit != requestlog.LimitHitErrorBurst ||
+			if line.LimitHit != requestlog.LimitHitMinuteRefusals ||
 				line.Offence != requestlog.OffenceLimit {
-				t.Errorf("log line has limit_hit %q and offence %q, want error_burst "+
+				t.Errorf("log line has limit_hit %q and offence %q, want minute_refusals "+
 					"and limit", line.LimitHit, line.Offence)
 			}
 
@@ -277,7 +277,8 @@ func TestErrorBurstOffOrAtItsDefault(t *testing.T) {
 				line = blockRule.send(s, client)
 			}
 
-			if broken := line.LimitHit == requestlog.LimitHitErrorBurst; broken != tc.broken {
+			broken := line.LimitHit == requestlog.LimitHitMinuteRefusals
+			if broken != tc.broken {
 				t.Errorf("the 31st refusal broke the error burst: %t, want %t",
 					broken, tc.broken)
 			}
@@ -306,8 +307,8 @@ func TestErrorBurstCountsEachClientTheChecksApplyTo(t *testing.T) {
 	blockRule.send(s, exempt)
 
 	line := blockRule.send(s, exempt)
-	if line.LimitHit != requestlog.LimitHitErrorBurst {
-		t.Errorf("log line has limit_hit %q, want error_burst", line.LimitHit)
+	if line.LimitHit != requestlog.LimitHitMinuteRefusals {
+		t.Errorf("log line has limit_hit %q, want minute_refusals", line.LimitHit)
 	}
 
 	s.get(exempt, http.StatusForbidden, requestlog.ActionTemporarilyBanned)
@@ -367,8 +368,8 @@ func TestObserveModeLogsAndAlertsTheErrorBurst(t *testing.T) {
 	line := s.request(client, blockedPath, http.StatusOK, requestlog.ActionForward)
 	wantWouldAction(t, line, requestlog.ActionBlockedByBlockRule)
 
-	if line.LimitHit != requestlog.LimitHitErrorBurst || line.BanExpires != "" {
-		t.Errorf("log line has limit_hit %q and ban_expires %q, want error_burst "+
+	if line.LimitHit != requestlog.LimitHitMinuteRefusals || line.BanExpires != "" {
+		t.Errorf("log line has limit_hit %q and ban_expires %q, want minute_refusals "+
 			"and none", line.LimitHit, line.BanExpires)
 	}