Fix typo in `PROCESSOR_MAPPING_NAMES` and add tests
# What does this PR do?

Fix typo in `PROCESSOR_MAPPING_NAMES` and add a new repo check: we check all names in auto (name) mapping are defined in the library.

The effect of this PR: (if `GITProcessor` is not fixed)

```bash
Checking all names in auto name mappings are defined.
Traceback (most recent call last):
  File "C:\Users\33611\Desktop\Project\transformers-hf-gcp\utils\check_repo.py", line 922, in <module>
    check_repo_quality()
  File "C:\Users\33611\Desktop\Project\transformers-hf-gcp\utils\check_repo.py", line 918, in check_repo_quality
    check_all_auto_object_names_being_defined()
  File "C:\Users\33611\Desktop\Project\transformers-hf-gcp\utils\check_repo.py", line 640, in check_all_auto_object_names_being_defined
    raise Exception(f"There were {len(failures)} failures:\n" + "\n".join(failures))
Exception: There were 1 failures:
`GITProcessor` appears in the mapping `PROCESSOR_MAPPING_NAMES` but it is not defined in the library.
```
_The documentation is not available anymore as the PR was closed or merged._<|||||>Failing test is irrelevant