It may be desirable to update all variables when a certain event occurs.
For example, some CDI clients may want all variabless updated when memory
is changed (when an ICDIMemoryChangedEvent is received) because it's
impractical or impossible for those backends to determine what specific
variables the memory change affected.
CDT will call this method to determine desired behavior for a limited set
of event types. The CDI backend should not expect to use this hook as a
general control mechanism for when variables are updated.
Whether the value for all active variables should be invalidated
and re-fetched from the CDI backend on the occurence of the given