[Metrics] UInt64Histogram does not honour custom boundaries

[sam-leitch-oxb]

If you CreateUInt64Histogram and add custom boundaries using a view, the counts output doesn't match the expected output.
Note CreateDoubleHistogram works as expected

This unit test can demonstrate the problem and expected output.

TEST(MeterProvider, UInt64HistogramBuckets)
{
  MeterProvider mp;
  auto m = mp.GetMeter("meter1", "version1", "schema1");

  std::unique_ptr<MockMetricExporter> exporter(new MockMetricExporter());
  std::shared_ptr<MetricReader> reader{new MockMetricReader(std::move(exporter))};
  mp.AddMetricReader(reader);

  std::shared_ptr<HistogramAggregationConfig> config(new HistogramAggregationConfig());
  config->boundaries_ = {10, 20, 30, 40};
  std::unique_ptr<View> view{new View("view1", "view1_description", AggregationType::kHistogram, config)};
  std::unique_ptr<InstrumentSelector> instrument_selector{
      new InstrumentSelector(InstrumentType::kHistogram, "histogram1")};
  std::unique_ptr<MeterSelector> meter_selector{new MeterSelector("meter1", "version1", "schema1")};
  mp.AddView(std::move(instrument_selector), std::move(meter_selector), std::move(view));

  auto h = m->CreateUInt64Histogram("histogram1", "histogram1_description", "histogram1_unit");

  h->Record(10, {});
  h->Record(20, {});
  h->Record(30, {});
  h->Record(40, {});
  h->Record(50, {});

  std::list<double> actual_boundaries;
  std::vector<uint64_t> actual_counts;
  reader->Collect([&](ResourceMetrics &rm) {
    for(const ScopeMetrics& smd : rm.scope_metric_data_) {
      for(const MetricData& md : smd.metric_data_) {
        for(const PointDataAttributes& dp : md.point_data_attr_) {
          auto data = opentelemetry::nostd::get<HistogramPointData>(dp.point_data);
          actual_boundaries = data.boundaries_;
          actual_counts = data.counts_;
        }
      }
    }
    return true;
  });
  ASSERT_EQ(std::list<double>({10, 20, 30, 40}), actual_boundaries);
  ASSERT_EQ(std::vector<uint64_t>({1, 1, 1, 1, 1}), actual_counts);
}

The output of this test is:

Expected equality of these values:
  std::vector<uint64_t>({1, 1, 1, 1, 1})
    Which is: { 1, 1, 1, 1, 1 }
  actual_counts
    Which is: { 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }

The boundaries_ values are correct, but the counts_ are wrong
16 count values is the expected size for the default set of boundaries, but the counts don't match default boundaries.

This has been tested against release 1.7.0, 1.8.1 and commit e7579ed

[lalitb]

#1869 fixes this.