Request tags, with refusing and limits per tag (closes #175)

Each request gets sorted tags from the lookup, new address lists, the
reputation sources and the rule matches, logged as `tags`. New settings:
`SWW_TAG_LISTS`, `SWW_TAG_DENY`, `SWW_TAG_LIMIT_PERCENT`. They replace
`SWW_ASN_LIMIT_PERCENT`, `SWW_COUNTRY_LIMIT_PERCENT` and
`SWW_DENIED_COUNTRIES`. New heuristics `tag_lists` and `tag_deny`; the
latter runs before the rate limits and again after the Core Rule Set.

Model: opus-5-5

internal/discriminator/discriminator_test.go

@@ -414,7 +414,7 @@ func TestReportNeverReachesAQuestionStillBeingHandled(t *testing.T) {
 
 	geojsURL, asked, release := startHeldGeoJS(t)
 	s := startDiscriminator(t, geojsURL, map[string]string{
-		lookupTimeout: "1h", deniedCountries: "kp", bytesLimitPerMinute: byteLimit,
+		lookupTimeout: "1h", tagDeny: denyKP, bytesLimitPerMinute: byteLimit,
 	})
 
 	first := s.question(siteA, client, "/")
@@ -765,7 +765,7 @@ func TestAllowCarriesTheLookupHeadersWhileTheSettingIsSet(t *testing.T) {
 
 			geojsURL, _ := startGeoJS(t)
 			s := startDiscriminator(t, geojsURL, map[string]string{
-				addLookupHeaders: tc.setting, lookupTimeout: "1h", deniedCountries: "kp",
+				addLookupHeaders: tc.setting, lookupTimeout: "1h", tagDeny: denyKP,
 			})
 
 			got := s.ask(fromDE, "/")