Missing external store target information #2502

External storage is not passing target information under the following uses:

• Activity heartbeat, worker-side: should pass either workflow or activity target depending on if the activity is a workflow activity or standalone activity
• Activity heartbeat, client-side: should pass either workflow or activity target depending on if the activity is a workflow activity or standalone activity; default to workflow if unable to determine.
• gRPC message-too-large: workflow target since failure generation is only done for too-large workflow task completions.

Nexus calls should have their own target type, but that should be logged separately and will require more plumbing.