Stop shadowing id-pkcs7-data OID

pkinit_crypto_openssl.c currently creates a shadow entry for
id-pkcs7-data so that OpenSSL will expect to see the corresponding
octet string in d.other instead than d.data.  This shadowing is very
unfriendly to other uses of OpenSSL and we should stop.  Eliminate the
shadowing and rewrite create_contentinfo so that it sets up the PKCS7
object correctly if the OID is id-pkcs7-data.

ticket: 7889
Use anonymous OIDs in pkinit_crypto_openssl.c

Stop adding OIDs to the global OpenSSL table.  It isn't thread-safe
(even with locking callbacks registered), and calling OBJ_cleanup
could break other uses of OpenSSL.  Instead, use anonymous OIDs
created with OBJ_txt2oid.  Anonymous OIDs need to be managed more
careful to avoid double-freeing, so create a copy before calling
PKCS7_add_signed_attribute, and don't free the result of
pkinit_pkcs7type2oid in cms_contentinfo_create.

ticket: 7889