Rename RKernel SDK modules

[ipetr0v]

This PR:

• Splits instance_attestation into attestation and crypto modules
  • Because attestation module will be removed once we have an Orchestrator for RKernel
  • And crypto module will contain the logic for both Instance and Group keys
• Renames mock_attestation to testing since it not only contains the attestation logic but also the crypto logic

[ipetr0v]

What is the migration plan for our clients?

Internal clients depend on a specific commit. So once we submit this PR, we would be able to update their code that reference them to the new commit

[jul-sh]

I don't have a strong objection to merging this.

But the rationale for the original naming choice of attestation that the provided crypto functions operate with keys that are specifically bound to the attestation. — Even if we remove the struct get the evidence itself, the signing and encryption keys are still bound to it.

@ipetr0v How would you want to handle group attestation if we support it in the future? The current mod was called instance_attestation, so we'd have the option of additionally offering an additional group_attestation mod in the future.

[ipetr0v]

I don't have a strong objection to merging this.

But the rationale for the original naming choice of attestation that the provided crypto functions operate with keys that are specifically bound to the attestation. — Even if we remove the struct get the evidence itself, the signing and encryption keys are still bound to it.

@ipetr0v How would you want to handle group attestation if we support it in the future? The current mod was called instance_attestation, so we'd have the option of additionally offering an additional group_attestation mod in the future.

There will be no group attestation, only group encryption. So GroupEvidenceProvider will not be there. And GroupKeyHandle will be in the crypto module.

Also I think from the point of view of our clients crypto is not a part of the attestation. It's definitely bound to it, but it's a separate logic on top of this.