Add exponential histogram support to CloudWatch PMD Exporter

[dricross]

Description of the issue

The Cloudwatch/PMD exporter currently drops all exponential histogram metrics.

Description of changes

Adds support for exponential histogram to the CloudWatch/PMD exporter

License

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

Tests

Setup something to what our OTLP -> AMP test does (see test repo).

Agent config:

{
  "agent": {
    "metrics_collection_interval": 15,
    "run_as_user": "root",
    "debug": true
  },
  "metrics": {
    "metrics_collected": {
      "otlp": {
        "http_endpoint": "127.0.0.1:1234"
      }
    }
  }
}

Use OTLP metrics and OTLP pusher from test repo to generate exponential histogram metrics.

In CloudWatch, we can see:

• min: 0
• max: 5
• sample count: 72
• Sum: 240

Requirements

Before commit the code, please do the following steps.

1. Run make fmt and make fmt-sh
2. Run make lint

[jefchien]

Are we trying to match the Distribution interface? It doesn't look like this would satisfy the interface as it is now. We would have to make the Distribution interface generic.

[jefchien]

nit: Instead of ignoring the lint, can we just not export the function? It doesn't look like it's used outside of this package.

[jefchien]

nit: If we store the unit in the MetricDatum already, why do we need to store it in the distribution?

[jefchien]

nit: Typo

Suggested change

	func (c *CloudWatch) buildMetricDataumExph(metric *aggregationDatum, dimensionsList [][]*cloudwatch.Dimension) []*cloudwatch.MetricDatum {
	func (c *CloudWatch) buildMetricDatumExph(metric *aggregationDatum, dimensionsList [][]*cloudwatch.Dimension) []*cloudwatch.MetricDatum {

[github-actions]

This PR was marked stale due to lack of activity.