Release v0.3.12 (#309)

New Features:
Add attest and verify command to gotpm #293
Add tee_technology flag and test for tee_technology flag #307
* intra-release breaking change

Other Changes:
Add OS Policy assignment tests for both debug and hardened. #301
Add a wrapper for ExternalTPM #302
Update to go-sev-guest v0.6.0 #304
Update base image family to use cos-dev #306
Update go-sev-guest to v0.6.1 #308