Optionally preprocess segmentation maps for MobileViT
Author: harisankar95
Pull request: yes

# What does this PR do?
- Preprocessor can now accept segmentations maps as well and performs augmentations inline to input images.
- Tests added for preprocessing segmentation masks.


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Comments:
@amyeroberts Can you please review the PR? MobileViT image preprocessor is updated to accept segmentation maps inline to other preprocessors for segmentation models like that of Segformer.  

I have corrected the error in the tests_torch.  I will wait for the https://github.com/huggingface/transformers/pull/28432 to be merged to fix the remaining CI tests

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_28420). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.