[Far Future] Make state syncs work with resharding

[gmilescu]

ND-469 created by None

[nikurt]

Agreed with @wacban that:

• It would be a significant effort to make this write
• After pre-state-root migration completes it's no longer needed.
  The conclusion was to skip this significant project and instead wait until for the pre-state-root migration to complete.

A minor change will be needed to how requests for state header or for state parts are interpreted. The nodes will need to assume that the ShardId in the request (or even better ShardUId) corresponds to the new ShardLayout, i.e. to the ShardLayout of the new epoch.

Pre-state-root migration will make it unnecessary to replay the last chunk of a shard, and will simplify the interaction of state sync and resharding.