Fix some broken doc links

Fix some broken doc links

Replace L<> link to header-file with a C<> reference.
Change some broken L<provider(3)> links to L<provider(7)>.
For consistency, rename four cipher pages to have a specific mode.
Fix up all references to any "generic" names to point to specific names.

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/10100)