Add "external" serde support to certificate chain types

[connorkuehl]

• Add serde support for CA Certificates
• Derive serde support for CA Chains
• Add serde support for SEV Certificates
• Derive serde support for SEV Chains
• Derive serde support for full certificate chain
• Derive serde support for launch::Start

[connorkuehl]

I've concluded my testing with serde_bytes and it does work. I've removed the hand-rolled serialize_seqs.