der: fix impl EncodeValue for &SequenceRef

[dishmaker]

Fixes &SequenceRef to match &OctetStringRef:

formats/der/src/asn1/octet_string.rs

Line 85 in de2aa55

impl EncodeValue for &OctetStringRef {

Adds test for SequenceRef from:

• der: breaking changes in ObjectIdentifier and AnyRef with tag_mode = IMPLICIT #1976

[baloo]

I'm not sure about this, that feels like a bug in the der_derive to me.

[dishmaker]

Even the constructor returns &Self:

formats/der/src/asn1/sequence.rs

Line 43 in f362dac

pub fn new(slice: &[u8]) -> Result<&Self> {

formats/der/src/asn1/octet_string.rs

Line 25 in f362dac

pub fn new(slice: &[u8]) -> Result<&Self, Error> {

[tarcieri]

Yeah, due to the blanket impls the ergonomics of reference types leave a bit to be desired.

That's a wart we can potentially smooth over in the next breaking release, possibly adding blanket impls for e.g. Borrow rather than concrete types to abstract over the discrepancy.