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/alerts/alerts_test.go

@@ -897,7 +897,7 @@ func TestDestinationThatDoesNotAnswerHoldsUpNeitherOther(t *testing.T) {
 		synctest.Wait()
 
 		wantDestinationCounts(t, q, alerts.DestinationSlack,
-			alerts.Counts{Sent: 3, Failed: 1})
+			alerts.Counts{Sent: 3, SendFailures: 1})
 
 		logged := log.String()
 		if !strings.Contains(logged,
@@ -934,7 +934,7 @@ func TestDropsAreCountedForEachDestination(t *testing.T) {
 		for destination, want := range map[string]alerts.Counts{
 			alerts.DestinationWebhook: {Sent: all},
 			alerts.DestinationSlack:   {Dropped: 1},
-			alerts.DestinationNtfy:    {Failed: all, Dropped: all},
+			alerts.DestinationNtfy:    {SendFailures: all, Dropped: all},
 		} {
 			wantDestinationCounts(t, q, destination, want)
 		}
@@ -1223,12 +1223,12 @@ func wantEvents(t *testing.T, webhook *standIn, want ...string) {
 // requests to it that it counts as failed, the alerts it counts as held
 // back, and those it counts as dropped for the webhook.
 func wantCounts(
-	t *testing.T, q *alerts.Queue, sent, failed, suppressed, dropped int64,
+	t *testing.T, q *alerts.Queue, sent, sendFailures, suppressed, dropped int64,
 ) {
 	t.Helper()
 
 	wantDestinationCounts(t, q, alerts.DestinationWebhook,
-		alerts.Counts{Sent: sent, Failed: failed, Dropped: dropped})
+		alerts.Counts{Sent: sent, SendFailures: sendFailures, Dropped: dropped})
 
 	if q.Suppressed() != suppressed {
 		t.Errorf("%d alerts held back, want %d", q.Suppressed(), suppressed)
@@ -1281,12 +1281,12 @@ func anAlertForEachEvent() []eventMessage {
 		},
 		{
 			alerts.Alert{
-				Event: alerts.EventWAFBlock, Client: netip.MustParseAddr("192.0.2.1"),
+				Event: alerts.EventCoreRuleSetMatch, Client: netip.MustParseAddr("192.0.2.1"),
 				Netblock: netip.MustParsePrefix("192.0.2.1/32"),
 				Reason:   "refused by the Core Rule Set",
 				Host:     "app.example",
 			},
-			"fsn1app1/blog: waf_block", "default shield",
+			"fsn1app1/blog: core_rule_set_match", "default shield",
 			"refused by the Core Rule Set\nhost: app.example\nclient: 192.0.2.1\n" +
 				"netblock: 192.0.2.1/32",
 		},