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

docs/state-files.md

@@ -64,8 +64,8 @@ since it was first seen:
 - body bytes of its requests, and of the responses it was sent;
 - responses by status class;
 - offences by kind: `limit`, `attack`, `blocked_by_block_rule` and
-  `waf_blocked`. A file may also hold `token_refused`, which is kept, and which
-  nothing adds to.
+  `blocked_by_core_rule_set`. A file may also hold `token_refused`, which is
+  kept, and which nothing adds to.
 
 ## `lookups.json`