Use `annotationlib` to simplify `test_official`

What kind of feature are you missing? Where do you notice a shortcoming of PTB?

Starting from Python 3.14, we can use annotationlib to refactor test_official to more properly work with annotations, specially forward references.

Describe the solution you'd like

Using annotationlib means we will require >=3.14 to run test official. IISC, annotationlib also resolves nested forward references, which is great for our use case.

Describe alternatives you've considered

Do patch work on existing codebase, but that's not a healthy practice.

Additional context

This recently came up in the #5259 PR where internal python API was changed, making it annoying to run the test official on 3.15.