apps/pkcs12: Change defaults from RC2 to PBES2 with PBKDF2

apps/pkcs12: Change defaults from RC2 to PBES2 with PBKDF2

Fixes #11672

Add "-legacy" option to load the legacy provider and
fall back to the old legacy default algorithms.

doc/man1/openssl-pkcs12.pod.in: updates documentation about the new
"-legacy" option

Signed-off-by: Sahana Prasad <sahana@redhat.com>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/12540)