Stateful SHA2_256: more lemmas to help proofs
Stateful SHA2_256: more lemmas to help proofs

mitls/hacl-star,mitls/hacl-star,mitls/hacl-star,mitls/hacl-star,mitls/hacl-star,mitls/hacl-star,mitls/hacl-star,mitls/hacl-star,mitls/hacl-star