Configuration-based use of HF hub-hosted datasets for training (#701)

* Add hf_dataset configuration for using HF hub-hosted datasets for (Q)LoRA training

* Pre-commit formatting

* Fix YAML config example

* Print DS info

* Include name

* Add hf_dataset parameter default

* Remove TextHFDataset and CompletionsHFDataset and use Dataset and CompletionsDataset instead, adding a text_key constructor argument to the former (and changing it to work with a provided data structure instead of just from a JSON file), and prompt_key and completion_key arguments to the latter with defaults for backwards compatibility.

* nits

* update docs

---------

Co-authored-by: Awni Hannun <awni@apple.com>

.circleci/config.yml

@@ -32,7 +32,7 @@ jobs:
             pip install --upgrade pip
             pip install unittest-xml-reporting
             cd llms/
-            pip install -e .
+            pip install -e ".[testing]"
       - run:
           name: Run Python tests
           command: |