Improve on Chacha20_vec specification to consider Low* model bounds
Improve on Chacha20_vec specification to consider Low* model bounds

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