[bnb] Introducing BitsAndBytesConfig (#21579)

* v1 `BitsandbytesConfig`

- add v1
- add tests
- more user-friendly API
- add docs

* change to `BitsAndBytesConfig`

* replace logic

* changes

* make fixup

* quality

* make fixup

* fix doc

* fix test

* update toctree

* fix slow test

* add tips

* add warning

* change title

* oops

* Update docs/source/en/main_classes/quantization.mdx

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* Update src/transformers/utils/bitsandbytes.py

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* remove unused file

* adapt suggestion

- add also tests
- change logic

* update docs

* adapt suggestions

---------

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

docs/source/en/_toctree.yml

@@ -199,6 +199,8 @@
       title: Pipelines
     - local: main_classes/processors
       title: Processors
+    - local: main_classes/quantization
+      title: Quantization
     - local: main_classes/tokenizer
       title: Tokenizer
     - local: main_classes/trainer