[loggingexporter] Fix display of bucket boundaries of exponential histograms

[alanwest]

The interval notation used for displaying bucket boundaries of exponential histograms was incorrect.

Should be:
Negative buckets -> lower bound is inclusive, upper bound exclusive
Positive buckets -> lower bound is exclusive, upper bound inclusive

See: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/data-model.md#exponential-buckets

The ExponentialHistogram bucket identified by index, a signed integer, represents values in the population that are greater than base**index and less than or equal to base**(index+1).

The positive and negative ranges of the histogram are expressed separately. Negative values are mapped by their absolute value into the negative range using the same scale as the positive range. Note that in the negative range, therefore, histogram buckets use lower-inclusive boundaries.