add class to scope in `get_type_hints`

from https://github.com/python/typing/issues/1820

would involve copying `get_type_hints` from `typing` and adding a single line to add the class object to the namespace + tests

The issue points to Python's typing.get_type_hints and the linked typing issue; start by comparing that implementation with this project's runtime components. Add the class object to the scope as described, then add tests to verify the behavior. Done means class-scoped names are handled correctly and the tests pass.

Written by the indexing model from the issue text.