[agent] Define schemas for attestation evidences negotiation

[ansasaki]

Description:

The first step before start pushing attestation evidences is the negotiation of evidence types and parameters. The agent needs to provide:

• TPM details (version, supported algorithms, signature schemes, attestation keys, etc.)
• Supported evidence types (IMA logs, UEFI logs, TPM quotes)

For each supported evidence type (e.g. IMA logs, UEFI logs, TPM quotes) a new type should be added. The added types should all be serializable using the serde crate to JSON format.

This is about defining the schema and implementing the types.

• Complete description: Attestation protocol
• Enhancement: 103: Agent-driven attestation
• Project board: https://github.com/orgs/keylime/projects/5

Checklist:

• The schema for the new types are defined and documented
• The schema for the new types include a field for a version to support future changes
• Documentation updated
• If configuration options are modified, the templates should be updated