函数 any_ecdsa_type 

pub fn any_ecdsa_type(
    der: &PrivateKeyDer<'_>,
) -> Result<Arc<dyn SigningKey>, Error>

Parse der as any ECDSA key type, returning the 第一个可用的

Both SEC1 (PEM section starting with ‘BEGIN EC PRIVATE KEY’) 并 PKCS8 (PEM section starting with ‘BEGIN PRIVATE KEY’) encodings are supported.