TYP ensure bool_t is always used in pandas/core/generic.py
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them

Currently, lots of methods use the `bool` annotation in that file. I'm not sure it affects `mypy` (some experiments with `reveal_type` suggest it doesn't) - however, it does confuse VSCode, which takes you to the method `bool` if you hover over one of these annotations.

The file already contains
```python
bool_t = bool  # Need alias because NDFrame has def bool:
```
(added in #26024), but it's not always used