feat(coderd/database/dbpurge): add retention for connection logs (#21022)

Add `DeleteOldConnectionLogs` query and integrate it into the `dbpurge`
routine. Retention is controlled by `--retention-connection-logs` flag.
Disabled (0) by default.

Depends on #21021
Updates #20743

coderd/database/queries/connectionlogs.sql

@@ -239,6 +239,18 @@ WHERE
 	-- @authorize_filter
 ;
 
+-- name: DeleteOldConnectionLogs :execrows
+WITH old_logs AS (
+	SELECT id
+	FROM connection_logs
+	WHERE connect_time < @before_time::timestamp with time zone
+	ORDER BY connect_time ASC
+	LIMIT @limit_count
+)
+DELETE FROM connection_logs
+USING old_logs
+WHERE connection_logs.id = old_logs.id;
+
 -- name: UpsertConnectionLog :one
 INSERT INTO connection_logs (
 	id,