Migrate `computeExclusiveDevDependencies` to `Pub`

Circumvents the implicitly reported bug in https://github.com/flutter/flutter/pull/158370.

https://github.com/flutter/flutter/blob/2efdc747920b5ce87dddbb4444a5ae7da8441ede/packages/flutter_tools/lib/src/dart/pub.dart#L28

