gh-141174: Improve `annotationlib.get_annotations()` test coverage (#141286)

* Test `get_annotations(format=Format.VALUE)` for stringized annotations on custom objects

* Test `get_annotations(format=Format.VALUE)` for stringized annotations on wrapped partial functions

* Update test_stringized_annotations_with_star_unpack() to actually test stringized annotations

* Test __annotate__ returning a non-dict

* Test passing globals and locals to stringized `get_annotations()`