keymgr: Bump ssh-key to 0.6.0.
This branch:
- brings in the ssh-key changes from #936 (closed) (by bumping ssh-key)
- changes the storage format used by the keymgr for x25519 client auth keys (from ed25519-ssh to our own custom key type, using
"x25519@torproject.org"
for the algorithm name). - implements
as_ssh_keypair_data
for x25519 keys.