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/alerts.md

@@ -9,9 +9,9 @@ back or dropped.
 - `ban`: a ban `discriminator` made.
 - `permanent_ban`: a permanent ban it made, or an existing ban made permanent by
   a request.
-- `waf_block`: the Core Rule Set scored a request at or over the threshold. The
-  request was refused unless the alert's `detail` gives `mode`: `detect` or
-  `observe`.
+- `core_rule_set_match`: the Core Rule Set scored a request at or over the
+  threshold. The request was refused unless the alert's `detail` gives `mode`:
+  `detect` or `observe`.
 - `anomaly`: a count over an anomaly threshold.
 - `reputation_hit`: a request from a client on a blocklist, the CrowdSec
   decision list or a DNS blocklist, or with an AbuseIPDB score that is a hit.
@@ -130,7 +130,7 @@ The priority and tag by event:
 
 - `ban`: priority `default`, tag `no_entry`.
 - `permanent_ban`: priority `high`, tag `no_entry`.
-- `waf_block`: priority `default`, tag `shield`.
+- `core_rule_set_match`: priority `default`, tag `shield`.
 - `anomaly`: priority `high`, tag `chart_with_upwards_trend`.
 - `reputation_hit`: priority `low`, tag `label`.
 - `source_failure` and `file_error`: priority `high`, tag `warning`.