update OpenSSH's Ed25519 code to the last version of SUPERCOP (20221122)

update OpenSSH's Ed25519 code to the last version of SUPERCOP (20221122)
and change the import approach to the same one we use for Streamlined
NTRUPrime: use a shell script to extract the bits we need from SUPERCOP,
make some minor adjustments and squish them all into a single file.

ok tb@ tobhe@