Fix changes that where changed to "new" from "merged"

Sometimes building merge commits have changed status of all changes being merged into "integrating" and if build fails into "new".

This should not happen anymore after: https://bugreports.qt.io/browse/QTQAINFRA-3029

But all changes, that were once merged and changed to "new", should be put back to "merged". There is a special admin api to do this.

Examples:

• https://codereview.qt-project.org/c/qt/qt3d/+/218085
• https://codereview.qt-project.org/c/qt/qt3d/+/236372