Support Ed25519 keys/certificates

[tambry]

The generic interface usage was added by 78712fe, which improved key format support.
ruby-openssl 3.0, shipped in Ruby 3.0, supports Ed25519 keys using the generic interface and returns a OpenSSL::PKey::PKey.
The only thing preventing these from working is a simple type check. Remove it and update various type annotations to refer to OpenSSL::PKey::PKey, though the old types will still work.

[joshcooper]

Hi @tambry thanks for you contribution! I think we'll need a few more changes to merge this:

1. Can you update the rake task for generating cert & key fixtures to generate an ED25519 private key and signed cert? It seems fine to reuse the test vectors from ruby or generate new private/pub keys, create a CSR and issue the cert using the intermediate CA's private key.
2. Run bundle exec rake gen_cert_fixtures to regenerate all of the fixtures, including the new key and cert. Best to create one commit for just those changes.
3. Next add unit tests for the new key, like we do for RSA and EC keys. You will probably need to do something like context 'using EC25519', if: RUBY_VERSION.to_f >= 3 && OpenSSL::OPENSSL_VERSION_NUMBER > 0x10101000 do so that the tests only run on Ruby and openssl versions >= 1.1.1.
4. This PR will now accept a bogus object as the private key, since we're now just checking that it's not an instance of DSA https://github.com/puppetlabs/puppet/pull/8869/files#diff-267828e88cef126d517addbead183553921e62648a51c9befa85dec6587357dbR129

I think it'd be better to only allow key types that we know work. The trouble is the OpenSSL::PKey::PKey#oid method doesn't exist in older ruby versions, so it'll need to be conditional. Maybe something like:

if !private_key.is_a?(OpenSSL::PKey::RSA) && \
   !private_key.is_a?(OpenSSL::PKey::EC) && \
   !(private_key.is_a?(OpenSSL::PKey::PKey) && private_key.respond_to?(:oid) && private_key.oid == 'ED25519')
  raise ...

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[joshcooper]

Hi @tambry changes look great! Could you rebase on main and resolve the ssl_provider conflict?

[tambry]

@joshcooper Sorry for the delay. I'll try to have a look at this within a few weeks.
We've been using this downstream for close to 2 years by now so it'd be lovely to get this upstreamed.

Last time I got hung up on updating the tests. I began, but getting a Ruby development environment setup proved a bit annoying as I couldn't simply grab the dependencies from my system package manager. I was also worried about breaking my whole Debian install so I began creating a separate rootfs, investigating how to use schroot with it and... then I dropped it. 😆

[joshcooper]

@tambry looks like there are some conflicts now. Could you rebase on main?

[tambry]

@joshcooper Thanks for the reminder, I've rebased. Note that the tests remain unfinished and are probably insufficient.

[joshcooper]

@tambry The ed25519 fixtures are missing, so tests are failing. Could you run bundle exec rake gen_cert_fixtures and add all of the updated cert/key fixtures? Also please include those update fixtures in this commit so it doesn't confuse git bisect later.