DelayedSnapshotJob may in parallel to any other workspace job and
triggers resource changes. Clients that rely on resource change events
(like JDT core) should have a chance to wait for possible pending
resource changes coming from this job.

Added a family to the job & a constant in the ResourcesPlugin.

See https://github.com/eclipse-jdt/eclipse.jdt.core/issues/2716#issuecomment-2268875660