Fix #[cgp_type] when associated types contain self-referential bounds

[soareschen]

This PR fixes a bug in #[cgp_type] where the associated type contains trait bounds that refer back to the associated type. For example:

#[cgp_type]
pub trait HasScalarType {
    type Scalar: Mul<Output = Self::Scalar> + Clone;
}

Before this, the Self::Scalar inside Mul<Output = Self::Scalar> is not transformed when the UseType and WithProvider providers are generated. The PR fixes the issue by binding it to a local associated type.

The same bug is also fixed for #[cgp_auto_getter] and #[cgp_getter] that contains an associated type. For example:

#[cgp_getter]
pub trait HasScalar {
    type Scalar: Mul<Output = Self::Scalar> + Clone;

    fn scalar(&self) -> &Self::Scalar;
}