Update the changelog and pubspec version for dart_internal

This is a follow-up for
https://dart-review.googlesource.com/c/sdk/+/436221

Change-Id: Ia6ba22782da7c0fe2148c5a11a528c20c6da51e9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/449960
Reviewed-by: Bob Nystrom <[email protected]>
Commit-Queue: Bob Nystrom <[email protected]>
Auto-Submit: Ivan Inozemtsev <[email protected]>

Author: iinozemtsev

pkg/dart_internal/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.2.16
+
+- Support the latest Dart SDK.
+
 ## 0.2.15
 
 - Support the latest Dart SDK.

pkg/dart_internal/pubspec.yaml

@@ -1,5 +1,5 @@
 name: dart_internal
-version: 0.2.15
+version: 0.2.16
 description: >-
   This package is not intended for wide use. It provides a temporary API to
   solve the problem: "Given an object some generic type A, how do I construct an