tools/testing/cxl: Add 'sanitize notifier' support

Allow for cxl_test regression of the sanitize notifier. Reuse the core
setup infrastructure, and trigger notifications upon any sanitize
submission with a programmable notification delay.

Cc: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>