Support unmarshalling JSON-formatted CloudWatch Metric Streams

[axw]

Component(s)

extension/encoding/awscloudwatchmetricstreamsencoding

Is your feature request related to a problem? Please describe.

I would like to be able to use the awscloudwatchmetricstreamsencoding extension to unmarshal JSON-formatted metrics from CloudWatch Metric Streams.

Describe the solution you'd like

Implement this:

opentelemetry-collector-contrib/extension/encoding/awscloudwatchmetricstreamsencodingextension/extension.go

Lines 46 to 49 in 7219cc4

	func (formatJSONUnmarshaler) UnmarshalMetrics([]byte) (pmetric.Metrics, error) {
	// TODO implement
	return pmetric.Metrics{}, fmt.Errorf("UnmarshalMetrics unimplemented for format %q", formatJSON)
	}

Describe alternatives you've considered

No response

Additional context

No response

[axw]

The logic can be extracted from https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/awsfirehosereceiver/internal/unmarshaler/cwmetricstream

The receiver should probably then depend on the extension package to have support for the encoding built-in.