[cm/prv/] with Classic McEliece 6960-119 + X25519.
=> https://classic.mceliece.org/ Classic McEliece
=> https://datatracker.ietf.org/doc/html/rfc7748.html X25519
Concatenation of Classic McEliece 6960-119 13948-byte private key
and X25519's 32-byte one.
"mceliece6960119-x25519" algorithm identifier is used.
