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/bans_test.go

@@ -415,7 +415,7 @@ func startWithClock(
 
 // sender sends requests to rproxy one after another, each on a connection of its
 // own, and checks each one's answer and log line. discriminatorAddr is where
-// discriminator's own endpoints are, which adminRequest asks. Every request
+// discriminator's own endpoints are, which ownEndpointRequest asks. Every request
 // discriminator gets must come through the sender, since the log lines are
 // matched to them in order.
 type sender struct {