Look into a dedicated scan executor for notification scans

Scanning for notifications is a continuous activity that Fluo does. It may make sense to do one of the following.

* Have a dedicated thread pool for notifcation scans with a small number of threads like Math.max(1,0.10 * numCores)
* Have a prioritizer that gives notification scans a lower priority.

Fluo could offer the prioritizer and/or dispatcher AND utilities or docs to configure them.

The issue names no files, tests, or entry points. Start by locating how notification scans are scheduled and how executor threads are configured; compare the dedicated thread-pool and prioritizer options. Done requires a decided approach plus a defined scope for any configuration utilities or documentation.

Written by the indexing model from the issue text.