Reference the non-"legacy" provider names directly from EVP_md5(3) &c.

Reference the non-"legacy" provider names directly from EVP_md5(3) &c.

Earlier today, it took me five manuals! to find what on earth the
"Performance"/"EVP_MD_fetch(3)" crosslinks actually mean:
  EVP_sha1(3)
  crypto(7)
  EVP_MD_fetch(3) (but not there! don't read that!)
  OSSL_PROVIDER-default(7)
  EVP_MD-SHA1(7)

If, instead, EVP_sha1(3) referenced EVP_MD-SHA1(7) at /all/,
which it should do, since it's supposed to be what you're replacing it
with, but it doesn't actually say that, maybe people would use it.
I know I didn't because it's basically just deadass buried

As found by git grep -l 'and should consider using'

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/22420)