* Restores ML Pods after M77.
* Fix Package.swift
* Refactor model info to be in-memory.
* Add improved model download functionality w/ single set of download handlers per task.
* Rename model download to better match URLSessionTask.
* Rename model download to better match URLSessionTask.
* Update unit test to read/write to user defaults.
* Minor updates to model downloader and tests.
* Use caches directory for model storage on tvOS.
* Change modelInfo to be privately settable.
