Support derivation of UseDelegate inside #[cgp_component]

[soareschen]

Summary

This PR introduces a new derive_delegate field for the #[cgp_component] family macros, allowing automated implementation of UseDelegate for CGP components.

Example

The updated ErrorRaiser component is defined as follows:

#[cgp_component {
    provider: ErrorRaiser,
    derive_delegate: UseDelegate<SourceError>,
}]
pub trait CanRaiseError<SourceError>: HasErrorType {
    fn raise_error(error: SourceError) -> Self::Error;
}

which would derive the following UseDelegate implementation, which previously had to be implemented manually:

#[cgp_provider(ErrorRaiserComponent)]
impl<Context, SourceError, Components, Delegate> ErrorRaiser<Context, SourceError>
    for UseDelegate<Components>
where
    Context: HasErrorType,
    Components: DelegateComponent<SourceError, Delegate = Delegate>,
    Delegate: ErrorRaiser<Context, SourceError>,
{
    fn raise_error(e: SourceError) -> Context::Error {
        Delegate::raise_error(e)
    }
}