der: fix derive(Sequence) on field: Vec<u8>

[dishmaker]

Fixes:

• der: Use #[asn1(type = "OCTET STRING")] with Vec<u8> #1539

Adds attribute:

• deref = "true"

#[derive(Sequence)]
pub struct MySequence {
    /// Without deref = "true" macro generates an error:
    ///
    /// the trait `From<Vec<u8>>` is not implemented for `BitStringRef<'_>`
    #[asn1(type = "OCTET STRING", deref = "true")]
    pub owned_bytes: Vec<u8>,
}

Is there any better way to add & ?