Spec v1.7.0-alpha.6 and Gloas genesis (#9190)

Co-Authored-By: Josh King <josh@sigmaprime.io>

Co-Authored-By: Jimmy Chen <jchen.tc@gmail.com>

Co-Authored-By: Michael Sproul <michael@sigmaprime.io>

beacon_node/beacon_chain/src/payload_envelope_streamer/tests.rs

@@ -72,6 +72,7 @@ fn build_chain(
                     execution_requests: Default::default(),
                     builder_index: 0,
                     beacon_block_root: block_root,
+                    parent_beacon_block_root: Hash256::ZERO,
                 },
                 signature: Signature::empty(),
             })