Cannot remove a project from a Batch if project was deleted from Octopus

[p-ob]

Two ways we could handle this:

1. On get of a batch with its batch items included, we could validate that the project it points to still exists
2. Allow UNLINKPROJ command to work for two scenarios:
   • Current: UNLINKPROJ batchIdOrName projectIdOrSlugOrName
   • New alternate: UNLINKPROJ batchItemId

We could use the new alternate in the UI with a delete button per batch item on the batch details page.