Relocate object resolution into hardcore.Post

This moves the object resolution step from where !127 (merged) added it into the hardcore.Post to match how the Python API performs the resolution.

The primary intent of this change is to prevent the automatic retrieval of large binary blobs for every message. Agents should trigger the object retrieval when they run a .Data() or .Metadata() method.

The restores core control listen and core control read functionality.

Additionally, to ensure this was working correctly, I have added core control download to the command line interface which retrieves binary blobs directly from the blackboard into a local file.