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/lookup_test.go

@@ -385,7 +385,7 @@ func TestRequestWaitsAsLongAsTheLookupTimeoutSays(t *testing.T) {
 		// is never reached.
 		const timeout = 3 * time.Second
 
-		server, out, _ := newDiscriminator(t, unansweredGeoJSURL, time.Now,
+		server, out, _ := newDiscriminator(t, silentGeoJSURL, time.Now,
 			map[string]string{
 				lookupTimeout:    timeout.String(),
 				allowedCountries: "DE",
@@ -405,25 +405,25 @@ func TestRequestWaitsAsLongAsTheLookupTimeoutSays(t *testing.T) {
 	})
 }
 
-// unansweredGeoJSURL is where a GeoJS that never answers is asked: a
+// silentGeoJSURL is where a GeoJS that never answers is asked: a
 // request to it waits, without the network, until it is abandoned.
 // TestMain registers it with Go's default transport, through which GeoJS
 // is asked.
-const unansweredGeoJSURL = "unanswered://geojs/v1/ip/geo.json"
+const silentGeoJSURL = "silent://geojs/v1/ip/geo.json"
 
 func TestMain(m *testing.M) {
 	transport, _ := http.DefaultTransport.(*http.Transport)
-	transport.RegisterProtocol("unanswered", unansweredGeoJS{})
+	transport.RegisterProtocol("silent", silentGeoJS{})
 	transport.RegisterProtocol("abuseipdb", abuseIPDBStandIn{})
 
 	m.Run()
 }
 
-// unansweredGeoJS is the GeoJS at unansweredGeoJSURL.
-type unansweredGeoJS struct{}
+// silentGeoJS is the GeoJS at silentGeoJSURL.
+type silentGeoJS struct{}
 
 // RoundTrip waits until req is abandoned.
-func (unansweredGeoJS) RoundTrip(req *http.Request) (*http.Response, error) {
+func (silentGeoJS) RoundTrip(req *http.Request) (*http.Response, error) {
 	<-req.Context().Done()
 
 	return nil, req.Context().Err()