Missing interface in RLC code generation

[v-jiaodi]

related issue: #3820

[v-jiaodi]

typespec:

model DefaultPets {
    catList?: CatDef[] = #[#{ catType: "American Shorthair" }];
}

model PetSettings {
    petList?: {
        cat?: DefaultPets.catList;
    };
}

model CatDef {
    catType: string;
}

interface Global {
    getPetSettings(): PetSettings;
}