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/refusallimit_test.go

@@ -191,7 +191,7 @@ func TestErrorBurstIsNotLoweredForAClientWithLowerLimits(t *testing.T) {
 		lookupTimeout:       "1h",
 		errorBurstThreshold: "2",
 		rulesDir:            writeRules(t, testRules),
-		countryLimitPercent: countryDEHalf,
+		tagLimitPercent:     countryTagDEHalf,
 	})
 
 	// Half of the threshold would be one, which the second refusal is over.