[TF-M] Design of symmetric key algorithms based Initial Attestation in TF-M

Hi all,

Hope you all well!

Profile Small (https://review.trustedfirmware.org/c/trusted-firmware-m/+/3598) includes symmetric key algorithm based Initial Attestation, as its Initial Attestation feature. I propose a design of symmetric key algorithm based Initial Attestation in TF-M, to complete the Profile Small feature list. Could you please take a look the design document at https://review.trustedfirmware.org/c/trusted-firmware-m/+/3898/? Any feedback is welcome!

I also upload a PoC of symmetric key algorithm based Initial Attestation in TF-M. Please check the patch set at https://review.trustedfirmware.org/q/topic:%22symmetric-attest%22+(status:op...).

Best regards, Hu Ziji