Add a compiler workaround for #908

[matanlurey]

Until #908 is fixed by dart-lang/sdk#32290, we will need to a little bit of our own type inference. I think we can do it safely in the following cases:

• The Provider type is either:
  • ClassProvider
  • ExistingProvider
  • FactoryProvider
  • ValueProvider
• The value of <provider>.token is an OpaqueToken<T> where T != dynamic

... we can "force" the OpaqueToken<T>'s T to be applied to Provider<T> for compilation, even though the analyzer thinks that T of Provider<T> is dynamic due to the SDK bug above.

That should be enough to unblock #908, and not cause any regressions.

[matanlurey]

Simplified this a bit, I won't check that it is a specific Provider type.

Negative, will do this!

[matanlurey]

Workaround was landed. Thanks!