DevTools 2.28.2 release notes

The 2.28.2 release of the Dart and Flutter DevTools includes the following changes among other general improvements. To learn more about DevTools, check out the DevTools overview.

This was a cherry-pick release on top of DevTools 2.28.1. To learn about the improvements included in DevTools 2.28.1, please read the release notes.

• Enabled DevTools extensions when debugging a Dart entry point that is not under lib (e.g. a unit test or integration test). Thanks to @bartekpacia for this change! - #6644

To find a complete list of changes in this release, check out the DevTools git log.