[cm/signed/] with SLH-DSA-SHAKE-256s with Merkle-tree hashing.

It is similar to [cm/signed/slh-dsa-shake-256s], but
[cm/hashed/shake-merkle] SHAKE256 Merkle-tree hashing is used.

"slh-dsa-shake-256s-merkle" algorithm identifier is used for the signature.
