Integrate leak_tracker

[Solido]

Leak Tracker is already integrated with Flutter but, counterintuitively, not with pure dart project where it could be important consolidation for long running programs.

Server-side or complexe desktops apps would be first citizen.

@polina-c is already on the subject and may need some short feature from the core team to deliver this awesome tool.

https://github.com/dart-lang/leak_tracker/issues/257

Thanks!