Add metric that characterizes [point estimate] discreteness

[sschmidt23]

** Feature request**
In fielding comments on the discreteness/periodicity in the FlexZBoost point estimates from members of the Clusters and LSS working groups, it occurred to me that having a metric that could quantify such "discreteness" effects at some level might be useful. For point estimate modes It think this would be looking for noticeably over-represented single value peaks, as we do evaluate the mode on a fixed grid, and thus many values will be identical. It might be slightly more complex for things like the mode or median, as values may not be identical. I don't have a particular metric/algorithm in mind, so comments with specific suggestions would certainly be welcome. This is also not a RAIL v1.0 requirement, just an enhancement that would be nice to have

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