LayoutLMv2FeatureExtractor now supports non-English languages when applying Tesseract OCR.
# What does this PR do?

This PR adds an additional `ocr_lang` argument to the \_\_init\_\_ method of LayoutLMv2FeatureExtractor  which specifies which Teserract model to use when applying Tesseract OCR.

Fixes #14511 

@NielsRogge
Can you verify the slow tests (which are not run by the CI) are passing as well?

i.e. `RUN_SLOW=yes pytest tests/test_feature_extraction_layoutlmv2.py` and `RUN_SLOW=yes pytest tests/test_feature_processor_layoutlmv2.py `<|||||>I assume you meant `RUN_SLOW=yes pytest tests/test_feature_extraction_layoutlmv2.py` and `RUN_SLOW=yes pytest tests/test_processor_layoutlmv2.py`?

I am developing on Windows, therefore my options when installing tesseract are limited to available installer versions. After moving from v5.0.0 to v4.1.0, which is the closest to v4.1.1, the version used to get bboxes in the `test_feature_extraction_layoutlmv2.py`, all of these tests ran successfully (There are no slow ones here).

As for `test_processor_layoutlmv2.py`, `test_processor_case1` failed for me, even when staying in the master branch. I was unable to reproduce the environment used to develop these tests on my computer. The reason is probably the different Tesseract version or model. The error comes from this line: https://github.com/huggingface/transformers/blob/3772af49ceba348f2c9c5bbbb7f7c12e35d2a6eb/tests/test_processor_layoutlmv2.py#L210