rpki-client: rework CRL handling

rpki-client: rework CRL handling

There is no benefit in parsing the CRLNumber in the RPKI. It is redundant
with other mechanisms, notably the requirements on manifests. rpki-client
never did anything with the CRL number anyway so stop parsing it in the
main process.

Move CRL AKI and CRL number handling from x509.c to crl.c, slightly improve
error checking for X509_CRL_get_ext_d2i() and only check well-formedness of
the CRL number: check it's there and non-critical. Avoid double warnings.

Add some checks for the well-formedness of the list of revoked certs.
Due to bugs in rpki-rs and Krill we can't reject empty lists (because
~15% of CRL's have this). And some people still use CRLs revoking certs
at the time they expire. This latter point might change mid-2025.

Add a hook for printing CRL numbers in file mode and warn about ill-formed
numbers (negative and overlong ones).

ok claudio job