Tests now share one Core Rule Set for each set of settings, loaded once
through sync.OnceValues in shared(). Exclusions-file tests and
TestCorazaWritesNoFile still load their own: loading is what they check.
Loading was not most of the time: the WordPress and Drupal recorded
requests, inspected one after another, were. Each recorded request now
runs as its own parallel subtest, with the same request and outcome.
Model: opus-5-5
sneak