Switch from mean to sum for histograms to simplify calculations #3
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…rying to merge two means
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The current logic for merging a histogram has some incorrect math for how the mean is merged. The end result of this is that the
sumcan go up and down causing all sorts of problems with histogram calculations,At the end of the day we don't really care about the
meanvalue the histogram only wants the sum. Instead of trying to properly merge twomeanvalues this PR switches to calculating the sum for the histogram and increasing that value as new data arrives. This should ensure an ever increasingsumas prometheus expects unless GCP produces a distribution with a negative mean which should hopefully never happen.