Support the latest test.

Release metatest 0.2.2+2.

The versions got kind of wonky for a while. This backfills the changelog
as best as possible to represent the versions actually released on
pub.dartlang.org. It also releases a new version with pending changes
included.

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//1946033002 .