Check all objects are equally in the main `__init__` file
# What does this PR do?

Add one more check in `check_repo.py` to further ensure objects are in the main `__init__`. (using our pytorch objects as the reference)

### Actions to take
(Do you agree @sgugger ?)

- The following should be added to the main `__init__`:

```bash
TFAutoModelForAudioClassification should be defined in the main `__init__` file.
TFAutoModelForMaskGeneration should be defined in the main `__init__` file.
TFAutoModelForMaskedImageModeling should be defined in the main `__init__` file.
```

- A fix is required:
```bash
TF_AutoModelForSemanticSegmentation should be defined in the main `__init__` 
file.
```
due to the mistake
```
TF_AutoModelForSemanticSegmentation = auto_class_update(
    TFAutoModelForSemanticSegmentation, head_doc="semantic segmentation"
)
```

- The following (the **pytorch** one) should be **removed** from the main `__init__`:
```bash
TFBertLayer should be defined in the main `__init__` file.
FlaxBertLayer should be defined in the main `__init__` file.
FlaxBigBirdLayer should be defined in the main `__init__` file.
TFLxmertEncoder should be defined in the main `__init__` file.
TFLxmertXLayer should be defined in the main `__init__` file.
TFMPNetLayer should be defined in the main `__init__` file.
TFMobileBertLayer should be defined in the main `__init__` file.
FlaxRoFormerLayer should be defined in the main `__init__` file.
TFSegformerLayer should be defined in the main `__init__` file.
TFViTMAELayer should be defined in the main `__init__` file.
```


_The documentation is not available anymore as the PR was closed or merged._<|||||>We cannot remove things from the main init, as it would be a breaking change. The `BertLayer` and the likes should never have been made public like this but it's too late now. And we shouldn't add the corresponding TF/Flax objects either, so this defeats the purpose of this new check.<|||||>I can add exceptional cases list though and not to touch those problematic entries.<|||||>Sure!