DOCS-26 - Metrics DPM - GA

[jpipkin1]

Purpose of this pull request

This pull request (PR) adds a release note and publishes the following beta article for GA release: https://help.sumologic.com/docs/metrics/metrics-dpm/

Ticket

DOCS-26

Select the type of change:

• [ ] Minor Changes - Typos, formatting, slight revisions
• [ ] Update Content - Revisions and updating sections
• [x] New Content - New features, sections, pages, tutorials
• [ ] Site and Tools - Updates, maintenance, and new packages for the site, Gatsby, React, etc

[jpipkin1]

@kimsauce or @JV0812, could you review this PR? The release is still a week away, but it would be nice to have the PR ready.

[jpipkin1]

Thanks for the quick review, @kimsauce!

[jpipkin1]

@angadrandhawa1, could you review this PR?