Unify Finalized Hash and number source.

- There are 4 place to get finalized hash:
  - `IBlockTree.FinalizedHash`.
  - `IBlockFinalizationManager`. 
  - `IBlockCacheService.FinalizedHAsh`.
  - `IFinalizedStateProvider`.
- Unify them.
- Note: `IFinalizedStateProvider.FinalizedBlockNumber` must work even if the block is not suggested yet or it will always become archive mode during forward sync.