Draft: Move TypeHint into a Python expression AST
Implement a subset of Python expr AST
Adds to the "name" construct a kind to distinguish global (global name that does not need to be resolved against the current module) vs local (names that needs to be resolved).
This consolidates the previous builtin/local/module construct by taking into account that modules can be relative (for example if in a #[pyclass] the user set `module=` to the submodule name)
Adds also the support for `Callable[[int], float]` and a beginning of constructs to represent constants (currently only None but will be useful for typing.Literal support)
TODO:
- update the macro code
- update the introspection code