fix: add registry credentials to instance component cosign Instance cosign sign/attest were missing --registry-username, --registry-password, and COSIGN_EXPERIMENTAL=1. Aligned with supply-chain component's .sign_image pattern.
fix: add registry credentials to instance component cosign Instance cosign sign/attest were missing --registry-username, --registry-password, and COSIGN_EXPERIMENTAL=1. Aligned with supply-chain component's .sign_image pattern.