feat: require finalization certificate in finalizer for last block of epoch

[matthias-wright]

This makes the finalization certificate that is sent from the syncer to the finalizer together with the last block of an epoch a requirement.

Changes:

• In the syncer, when trying to dispatch a block to the finalizer, a check is added to ensure that the finalization certificate is available. If it is not available, a request is sent via the resolver.
• The finalization certificate that is sent from the syncer to the finalizer is still wrapped in an Option. The reason for this is that for every block of an epoch, except the last one, no finalization is sent.
• In the finalizer's handle_finalized_block method, we expect the finalization certificate for the last block of an epoch.
• Finalizer tests and binary e2e tests are updated