[pkg/otlp/model] Backport translator changes

[mx-psi]

What does this PR do?

This PR backports two recent changes on the OpenTelemetry Collector Datadog exporter version of this module:

• [exporter/datadogexporter] Improve reset detection on cumulative metrics open-telemetry/opentelemetry-collector-contrib#6120
• [datadogexporter] [Breaking change] Make distributions the default histogram export option open-telemetry/opentelemetry-collector-contrib#5885

Motivation

Keep the two versions in sync until we can drop the code from the Datadog exporter side.

Additional Notes

To do this I copied the code from the main branch on the Collector and replaced the imports. diff between the translator code and the Collector translator code as of commit open-telemetry/opentelemetry-collector-contrib@e066c9c:

diff -u pkg/otlp/model/translator/metrics_translator.go /Users/pablo.baeyens/Source/otel/opentelemetry-collector-contrib/exporter/datadogexporter/internal/translator/metrics_translator.go
--- pkg/otlp/model/translator/metrics_translator.go     2021-11-08 13:18:11.000000000 +0100
+++ opentelemetry-collector-contrib/exporter/datadogexporter/internal/translator/metrics_translator.go 2021-11-08 13:16:32.000000000 +0100
@@ -24,9 +24,9 @@
        "go.opentelemetry.io/collector/model/pdata"
        "go.uber.org/zap"
 
-       "github.com/DataDog/datadog-agent/pkg/otlp/model/attributes"
-       "github.com/DataDog/datadog-agent/pkg/otlp/model/internal/instrumentationlibrary"
-       "github.com/DataDog/datadog-agent/pkg/otlp/model/internal/utils"
+       "github.com/open-telemetry/opentelemetry-collector-contrib/exporter/datadogexporter/internal/attributes"
+       "github.com/open-telemetry/opentelemetry-collector-contrib/exporter/datadogexporter/internal/instrumentationlibrary"
+       "github.com/open-telemetry/opentelemetry-collector-contrib/exporter/datadogexporter/internal/translator/utils"
 )
 
 const metricName string = "metric name"
diff -u pkg/otlp/model/translator/metrics_translator_test.go /Users/pablo.baeyens/Source/otel/opentelemetry-collector-contrib/exporter/datadogexporter/internal/translator/metrics_translator_test.go
--- pkg/otlp/model/translator/metrics_translator_test.go        2021-11-08 13:18:11.000000000 +0100
+++ opentelemetry-collector-contrib/exporter/datadogexporter/internal/translator/metrics_translator_test.go    2021-11-08 13:16:32.000000000 +0100
@@ -30,7 +30,7 @@
        "go.uber.org/zap/zapcore"
        "go.uber.org/zap/zaptest/observer"
 
-       "github.com/DataDog/datadog-agent/pkg/otlp/model/attributes"
+       "github.com/open-telemetry/opentelemetry-collector-contrib/exporter/datadogexporter/internal/attributes"
 )
 
 func TestGetTags(t *testing.T) {
Only in opentelemetry-collector-contrib/exporter/datadogexporter/internal/translator/: utils

Describe how to test your changes

To test open-telemetry/opentelemetry-collector-contrib#6120:

1. Setup an OTLP-producing program that generates a cumulative histogram and a cumulative sum (e.g. with the Histogram and Counter instruments with default settings).
2. Send a constant amount per collection period (e.g. increase the value by 10 on every collection period).
3. Check that the graph on the Datadog's webapp looks constant
4. Restart the application (but not the Agent); check that there are no spikes on the webapp graph.

One can also add a negative amount with the counters histogram mode and check that the sum is non 0.

open-telemetry/opentelemetry-collector-contrib#5885 doesn't need testing (only adds unit tests on this module)

Checklist

• A release note has been added or the changelog/no-changelog label has been applied.
• The need-change/operator and need-change/helm labels has been applied if applicable.
• The appropriate team/.. label has been applied, if known.
• If known, an appropriate milestone has been selected; otherwise the Triage milestone is set.
• The config template has been updated if applicable.

Note: Adding GitHub labels is only possible for contributors with write access.

[mx-psi]

This and the comment above were changed on #9398 but are still unchanged on the contrib repo

[mx-psi]

This comes from open-telemetry/opentelemetry-collector-contrib/pull/5315