Leverage flutter-fix for breaking changes in one-isolate

[ryanheise]

Is your feature request related to a problem? Please describe.

The one-isolate contains quite a number of breaking changes which may make migration a hassle.

Describe the solution you'd like

Use flutter-fix to allow developers to automatically migrate code in simple cases.

Describe alternatives you've considered

There are other things we can do "in addition to" flutter fix to make the migration easier, but they are not mutually exclusive.

Additional context

[ryanheise]

flutter-fix unfortunately turns out to be a bit too limited. It can rename method invocations, but not method overrides, so it cannot rename onPlay to play.

I will remove this from the 0.18.0 milestone and instead focus on expanding the backwards compatibility layer.