feat(pkcs11-tool): print serial number when reading certificates

[AlexandreGonzalo]

I am using the pkcs11-tool to list the certificates stored in my PKCS#11 token.
I have this patch which displays the certificate serial number and maybe that's something which could be merged to master.

Certificate Object; type = X.509 cert
subject: DN: C=FR, ST=PACA, L=Valbonne, O=Trustonic, CN=*.trustonic.com
serial: 54E67E7F3DB8F07D11D473717C71E057FD7D22C9
ID: 01

Checklist

• Documentation is added or updated
• New files have a LGPL 2.1 license statement
• PKCS#11 module is tested
• Windows minidriver is tested
• macOS tokend is tested

[Jakuje]

From answer to @frankmorgner comment in #2630

can we do this without being dependant on OpenSSL?

I did the same as getSUBJECT() above and it is an easy win.
I don't think that it is worth to try to avoid OpenSSL.

I think this is ok as we already use the openssl to parse the SUBJECT. In any case, most of the builds are using OpenSSL anyway now.

I think this is good to go also for 0.23.0

[Jakuje]

Thank you. Merging.