Add Fast Image Processor for LayoutLMv2 (#37203)

* add support layoutlmv2

* make style

* Apply suggestions from code review

Co-authored-by: Yoni Gozlan <74535834+yonigozlan@users.noreply.github.com>

* add warning and clean up

* make style

* Update src/transformers/models/layoutlmv2/image_processing_layoutlmv2_fast.py

Co-authored-by: Yoni Gozlan <74535834+yonigozlan@users.noreply.github.com>

---------

Co-authored-by: Yoni Gozlan <74535834+yonigozlan@users.noreply.github.com>

docs/source/en/model_doc/layoutlmv2.md

@@ -310,6 +310,11 @@ print(encoding.keys())
 [[autodoc]] LayoutLMv2ImageProcessor
     - preprocess
 
+## LayoutLMv2ImageProcessorFast
+
+[[autodoc]] LayoutLMv2ImageProcessorFast
+    - preprocess
+
 ## LayoutLMv2Tokenizer
 
 [[autodoc]] LayoutLMv2Tokenizer