Add option to merge exponential histograms without upscaling #137674
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kkrik-es
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With our current algorithm, we upscale exponential histograms before merging them to prevent single mis-configured histograms from dragging down the overall accuracy.
However, this up-scaling can introduce a tiny bit of error to the up-scaled histogram, therefore it should not be used when merging intermediate results (e.g. merging histograms which were already merged together at the data-nodes).
This PR simply adds a method to do this alongside with a test.