Remove UnitExplicitTopLevelAccessors, UnitExplicitTopLevelVariables.
Remove UnitExplicitTopLevelAccessors, UnitExplicitTopLevelVariables.

Change-Id: Ic7273cca19e98f47b7ef4a3cf62ded9b0a51bed1
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/122305
Reviewed-by: Samuel Rawlins <5cf2cac5eec2ad6d0eb2b0f4ff6af9a590ce2bf6@google.com>
Commit-Queue: Konstantin Shcheglov <09e4d7516628963212bf4aace2f97603d2b706e4@google.com>

dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk