New `TypeInfo` struct and `PyStubType` trait

[termoshtt]

• Resolve #16, remove the dependency to "PyO3/experimental-inspect"
• New TypeInfo is introduced which replace pyo3::inspect::types::TypeInfo. It is generated by PyStubType traits.
• Impelement PyStubType to
  • builtins (u32, i32, String, ...)
  • Collections (Vec<T>, HashMap<K, V>, ...)
  • PyO3 primitives (PyAny, PyList, PyDict)
• Helper for implementing PyStubType for user struct, i.e. #[derive(PyStubType)] will be next PR.