apps: Change default cipher to aes-256-cbc for req, cms and smime apps

apps: Change default cipher to aes-256-cbc for req, cms and smime apps

Update `CHANGES.md` and `NEWS.md`; remove `no-des` guard from req, cms,
and smime apps

Update MAN pages for default cipher; fix styling by removing braces around single statements

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/25839)