make Ed25519 master key, signing key and cert ascii-armored on disk by default
As discussed in legacy/trac#16645 (moved): (Ed25519 key backups) printing it on paper, QR codes, email, cloud, portable storage media, backup servers, you name it should all be possible for an user.
I suggest using Base58Check encoding (it removes 0OIl chars) - makes it easier to re-create the key from a paper printed version of it.
An ascii-armored version for the key files should be used by default regardless if the master Ed25519 key is encrypted with a passphrase or not.