Implement AddBlock using translated shim type backed by Ext

[timwu20]

Issue Summary

Taken from design doc:

Given that storing a block and it's associated storage changes are handled in one BlockImportOperation, we should remove the StoreTrie method entirely from StorageState. Rather BlockState.AddBlock should accept an introduced OverlayedChanges type analogous to the substrate primitive.

Acceptance Criteria

• Modify AddBlock method in BlockState interface to accept OverlayedChanges
• Implement AddBlock method in translation shim to take OverlayedChanges. Eventually call BlockImport methods from issue Implement BlockImport interface for Client type #4458 to taken in parent block hash, and storage changes from OverlayedChanges to import block.
• Unit tests