feat(injector): make DI3 compatible with DI2

I don't get exactly what this code is for.

Will it be possible to list parametrized class in `@Injectables` now (provided this is the issue you are trying to fix) ?

Is this a fix or a feature ? Should it have tests ?

"workaround" makes me think that there will be a better way to fix this in the future, is my understanding corect ?