Merge modules-next onto keys-pqc, fixing up sign-file.c

Merge the removal of support for PKCS#7 signatures (CMS is still available)
in the modules tree onto the addition of ML-DSA support.  There are
conflicting changes in sign-file.c, including the removal of a variable
(use_signed_attrs) in the modules tree which is necessary for ML-DSA
support until OpenSSL-4 is widely available (v3.5 doesn't support
CMS_NOATTR with ML-DSA).

Signed-off-by: David Howells <dhowells@redhat.com>