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/anomaly_test.go

@@ -73,7 +73,7 @@ func TestEachScopeAndWindowOverItsThresholdAlertsOncePerCooldown(t *testing.T) {
 		{anomalyASN, anomaly.ScopeASN, netip.Prefix{}, asnDE, map[string]any{"asn": asnDE}},
 		{anomalyTotal, anomaly.ScopeTotal, netip.Prefix{}, "the whole service", nil},
 		{
-			anomalyWatch, anomaly.ScopeWatch, netip.MustParsePrefix(clientsNet),
+			anomalyWatch, anomaly.ScopeWatchedNet, netip.MustParsePrefix(clientsNet),
 			"the named netblock office, " + clientsNet, map[string]any{"name": "office"},
 		},
 	} {