The GRANDPA light-client logic and storage is updated to maintain a history of authorities set changes. This feature is necessary to support a more robust system, especially for evidence checks. In the previous version, the client could only store the current authorities, preventing it from correctly verifying whether misbehavior had taken place when a set change occurs.

The history of authorities is stored in the client state, with information of the block height, the timestamp of changes, the new set id and the new authorities.

This commit also enhances the misbehaviour detection functionality by checking every header in the submitted headers for evidence instead of only the first few unknown headers.

Additional fixes contain correcting the finality proof verification for client update and modifying relevant test logic accommodating the new client features.

…authorities

…ties' into vmarkushin/grandpa-track-authorities