restartableTask Should Populate Existing Task Types

[rtablada]

Currently trackedTask is showing a value of unknown without explicit types.

Ember concurrency allows teams to define Task return types already (or even have them inferred) so it would be nice for this to bubble through to trackedTask in order to reduce the excess flow of types and allow the use of inferred types (which would also allow typing to happen at the source instead of manual checks all the way through).

In the place where teams do choose to manually type their trackedTasks, this should in theory also give type checking in the case where the passed in task arg does not match the expected type signature

[NullVoxPopuli]

sounds like a good thing to fix/support!