Name log fields, metrics and the Core Rule Set package for what they are (closes #192)

Log field, metric, action and event names now say what they count
and, for timings, the unit. Package internal/waf is internal/coreruleset.

Model: opus-5-5

internal/discriminator/admin.go

@@ -42,7 +42,7 @@ var (
 
 // answerHealth answers a request for the health endpoint.
 func (rq *request) answerHealth() {
-	rq.line.Action = requestlog.ActionAdmin
+	rq.line.Action = requestlog.ActionOwnEndpoint
 	// Set here rather than left to Go's server, which would set it only
 	// after the log line has taken the response's headers.
 	rq.out.Header().Set("Content-Type", "text/plain; charset=utf-8")
@@ -55,7 +55,7 @@ func (rq *request) answerHealth() {
 // refused with 401. An endpoint whose token is unset answers 404, as any other
 // path does.
 func (rq *request) answerAdmin() {
-	rq.line.Action = requestlog.ActionAdmin
+	rq.line.Action = requestlog.ActionOwnEndpoint
 
 	token, answer := rq.endpoint()