Keyring should have a fix encoding

[matteo-cristino]

Some keys in the keyring follow the CONF encoding during the output phase:

Zenroom/src/lua/zencode_keyring.lua

Lines 186 to 190 in d08d516

	if obj.dilithium then res.dilithium = CONF.output.encoding.fun(obj.dilithium) end
	if obj.kyber then res.kyber = CONF.output.encoding.fun(obj.kyber) end
	if obj.schnorr then res.schnorr = CONF.output.encoding.fun(obj.schnorr) end
	if obj.ntrup then res.ntrup = CONF.output.encoding.fun(obj.ntrup) end
	if obj.eddsa then res.eddsa = O.to_base58(obj.eddsa) end

while in the input there is only a fixed encoding (for the above is base64).
I think that generally it is better if the keyring encoding is fixed, so that we are alsways sure with what type of encoding we have to load the key.

[jaromil]

In cass we fix the encoding then base64 is preferred as requiring less changes, also is the most interoperable from shell scripts.