refactor(contract): move TEE attestation lifecycle into api/attestation.rs (#4197)

Author: gilcu3

crates/contract/src/api.rs

@@ -1,5 +1,6 @@
 //! The contract's entrypoint surface, one module per feature.
 
+pub mod attestation;
 pub mod authorization;
 pub mod ckd;
 pub mod common;