Metrics SDK: Add Metrics Exporter

[lalitb]

Specs: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#metricexporter

The specification defines both push and pull metric exporters. These interfaces will need to be defined so that exporters can implement them. ( https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#interface-definition )

• The exporters should receive a list of Metrics
• Metric contains name, unit, description, meter information, etc, and a list of MetricPoints
• MetricPoint contains timestamps, dimensions, value (or buckets), exemplars, etc, of collected metrics

[github-actions]

This issue was marked as stale due to lack of activity. It will be closed in 7 days if no furthur activity occurs.

[lalitb]

#1312 closes this