Test database schema stability (#7669)

This PR implements some heuristics to check for breaking database changes. The goal is to prevent accidental changes to the database schema occurring without a version bump.

beacon_node/beacon_chain/tests/main.rs

@@ -7,6 +7,7 @@ mod events;
 mod op_verification;
 mod payload_invalidation;
 mod rewards;
+mod schema_stability;
 mod store_tests;
 mod sync_committee_verification;
 mod tests;