TensorFlow Official Models 2.11.0

This release of the Official Models targets TensorFlow 2.11.0. Note that Research/tutorial/sample models have been removed.

New features:

1. MobileNetV2 backbone for Mask RCNN
2. Panoptic deeplab supported;
3. freeze_backbone supported, and many bug fixes
4. FNet and SparseMixer implementations
5. Move ViT models from projects to vision main backbone folder

Release branch is: https://github.com/tensorflow/models/tree/r2.11