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/ratelimits.go

@@ -28,12 +28,14 @@ func (rateLimits) check(_ context.Context, rq *request, now time.Time) *verdict
 		return nil
 	}
 
-	rq.limitPercent, rq.bytesPercent = rq.limitPercentages()
-	rq.line.LimitPercent, rq.line.LimitPercentSetting = rq.limitPercent.logged()
-	rq.line.BytesPercent, rq.line.BytesPercentSetting = rq.bytesPercent.logged()
+	rq.rateLimitPercent, rq.bytesLimitPercent = rq.limitPercentages()
+	rq.line.RateLimitPercent, rq.line.RateLimitPercentSetting =
+		rq.rateLimitPercent.logged()
+	rq.line.BytesLimitPercent, rq.line.BytesLimitPercentSetting =
+		rq.bytesLimitPercent.logged()
 
 	counts, hit, over := rq.h.limiter.Count(rq.h.clientGroup(rq.client), now,
-		rq.limitPercent.percent)
+		rq.rateLimitPercent.percent)
 	rq.line.Counts = counts
 
 	if !over {