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

Log field, metric, action and event names now say what they count
and, for timings, the unit. Package internal/waf is internal/coreruleset.

Model: opus-5-5

internal/alerts/alerts_test.go

@@ -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",
 		},