Method to_csharp_ident_upper

crates/csharp/src/csharp_ident.rs:103–110

(&self)

    }

    fn to_csharp_ident_upper(&self) -> String {
        // Escape C# keywords
        if Self::csharp_keywords().contains(&self) {
            format!("@{self}")
        } else {
            self.to_upper_camel_case()
        }
    }
}