IPv6 IPs in host certificates for dual-stack management interfaces

[psafont]

Adds IPv6 addresses to host certificates when their management interfaces are configured to use Dual stack.

I've tested manually on IPv4-only hosts, and the certificates are generated in the same way as before.
I've run the smoke and verification tests (Suite Run 215863), all of them passed

@last-genius you probably want to test these changes, run openssl x509 -text -in /etc/xensource/xapi-ssl.pem on a dual host, and see that it contains the IPv6 and IPv4 addresses.

[stormi]

We have tests here which can install two hosts in IPv6 and then join them in a pool. Would this be a sufficient check?

(However running them is not really straightforward at the moment, so a manual test might be better for this PR. For future regression testing with IPv6, my question remains)

[psafont]

We have tests here which can install two hosts in IPv6 and then join them in a pool. Would this be a sufficient check?

I think so, yes. Do the test also inspect certificates?

[lindig]

Extended and clever use of Option.fold

[stormi]

I think so, yes. Do the test also inspect certificates?

I don't think so. Also we don't test dual stack yet 😬 (seen the title update)

[last-genius]

I think so, yes. Do the test also inspect certificates?

I don't think so. Also we don't test dual stack yet 😬 (seen the title update)

I will test it manually then on Monday

[last-genius]

xapi on a dualstack host without this PR:

Certificate:
    Data:....
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: CN=10.1.19.21
        Validity...
        Subject: CN=10.1.19.21
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (2048 bit)
                Modulus:  ...
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Subject Alternative Name:
                DNS:xcp-ng-asvds, IP Address:10.1.19.21

with this PR:

Certificate:
    Data: ...
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: CN=xcp-ng-asvds
        Validity ...
        Subject: CN=xcp-ng-asvds
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (2048 bit)
                Modulus: ....
                Exponent: ...
        X509v3 extensions:
            X509v3 Subject Alternative Name:
                DNS:xcp-ng-asvds, IP Address:10.1.19.21, IP Address:2A01:240:AB08:5:19:0:0:21

[psafont]

I didn't expect the issuer and the subject to change. I'm not sure what we want to do here, at some level it makes sense to use the DNS name if possible, the IPs are still available in the SAN anyway.

I checked the code, and the hsotname should be preferred since 2021, in 7ca6ea4