Recursive enum type does not know its name (minor)

[ChristopherRabotin]

Bug Description

Recursive enum types were introduced in #4694 (thanks!). They work when explicitly referencing the enum's name, but when it's referred as Self PyO3 cannot recognize it.

For example, the works fine:

#[pyclass]
enum TestRecursiveEnum {
    WithRec { my_field: Py<TestRecursiveEnum> },
}

But this leads to a compilation error:

#[pyclass]
enum TestRecursiveEnum {
    WithRec { my_field: Py<Self> },
}

error[E0308]: mismatched types
  --> anise-py/src/astro.rs:37:15
   |
37 |     WithRec { my_field: Py<Self> },
   |               ^^^^^^^^ expected `Py<TestRecursiveEnum>`, found `Py<TestRecursiveEnum_WithRec>`
   |
   = note: expected struct `pyo3::Py<TestRecursiveEnum>`
              found struct `pyo3::Py<TestRecursiveEnum_WithRec>`

error[E0308]: mismatched types
    --> anise-py/src/astro.rs:37:15
     |
35   | #[pyclass]
     | ---------- arguments to this function are incorrect
36   | enum TestRecursiveEnum {
37   |     WithRec { my_field: Py<Self> },
     |               ^^^^^^^^ expected `&Py<TestRecursiveEnum_WithRec>`, found `&Py<TestRecursiveEnum>`
     |
     = note: expected reference `&pyo3::Py<TestRecursiveEnum_WithRec>`
                found reference `&pyo3::Py<TestRecursiveEnum>`
note: associated function defined here
    --> /home/chris/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/pyo3-0.25.1/src/impl_/pyclass.rs:1440:12
     |
1440 |     pub fn convert_field<'a, 'py, T>(obj: &'a T, py: Python<'py>) -> PyResult<Py<PyAny>>
     |            ^^^^^^^^^^^^^

For more information about this error, try `rustc --explain E0308`.
error: could not compile `anise-py` (lib) due to 2 previous errors

Steps to Reproduce

1. Define a recursive type with Self in the field (cf. description)
2. Build

Your operating system and version

Linux, Opensuse Tumbleweed

Your Python version (python --version)

3.11.12

Your Rust version (rustc --version)

1.88

Your PyO3 version

0.25.1

How did you install python? Did you use a virtualenv?

Virtualenv

Additional Info

No response