Currently, the only way to tell if a path is available for histogram CE is via StatsCatalog::getHistogram(). However, it is inefficient to confirm the availability via trial-and-error.

To allow CBR easier to determine if a path is available for histogram CE, this ticket suggest to expose an API to return the set of available field paths. The implementation can be filing a FindRequest to system collection and then cache the results (like getHisotgram() does today).