[infra] Print details of unapproved (new or previous) failures in build failure message
[infra] Print details of unapproved (new or previous) failures in build failure message

Change-Id: Ic9f9151f5884b636b902b5ba6b7d2c35cec6417b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/138287
Reviewed-by: Karl Klose <49bc0b76cffb0b10cd8c84f9cabc97a31ffe6343@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk