OnExceptionCheckpoint: training resumes if ckpt found, even if no ckpt_path provided

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### Bug description

- The [documentation of `Trainer.fit`](https://lightning.ai/docs/pytorch/stable/common/trainer.html#fit) states training will only be resumed if `ckpt_path` is provided.
- The [documenation of `OnExceptionCheckpoint`](https://lightning.ai/docs/pytorch/stable/api/lightning.pytorch.callbacks.OnExceptionCheckpoint.html#onexceptioncheckpoint) states it's purpose is to save a checkpoint on exception.

However, if an `OnExceptionCheckpoint` is provided to the trainer's list of callbacks, then even if `Trainer.fit` is called without providing `ckpt_path` argument then the `CheckpointConnector` will search for a checkpoint in `OnExceptionCheckpoint.dirpath`, and if one is found it will be used to resume training.

Further, the warnings shown at the beginning of `Trainer.fit` when `OnExceptionCheckpoint` callback is enabled IMO are incorrect, (see logs below)

### What version are you seeing the problem on?

v2.2

### How to reproduce the bug

```python
from lightning.pytorch.callbacks import OnExceptionCheckpoint, ModelCheckpoint
from lightning.pytorch import Trainer
from lightning.pytorch.demos.boring_classes import BoringModel

trainer = Trainer(
# NOTE: either of these callback lists reproduce the issue, (and same warnings mentioned below)
# callbacks=[OnExceptionCheckpoint("."), ModelCheckpoint(".", save_last=True)],
callbacks=[OnExceptionCheckpoint("."), ModelCheckpoint(".", save_last=False)],
max_epochs=3,
)
trainer.fit(model=BoringModel())

# calling `fit` again will result in resumed training from discovered checkpoint in cwd:
trainer.fit(model=BoringModel())
```

### Error messages and logs

The following warnings are confusing and arguably wrong:

```
.../checkpoint_connector.py:126: `.fit(ckpt_path=None)` was called without a model. The last model of the previous `fit` call will be used. You can pass `fit(ckpt_path='best')` to use the best model or `fit(ckpt_path='last')` to use the last model. If you pass a value, this warning will be silenced.
.../checkpoint_connector.py:186: .fit(ckpt_path="last") is set, but there is no last checkpoint available. No checkpoint will be loaded. HINT: Set `ModelCheckpoint(..., save_last=True)`.```

### Environment

```
PyTorch Lightning Version: 2.2.1
```

### More info

_No response_

cc @lantiga

Start with Trainer.fit and the CheckpointConnector warnings referenced at checkpoint_connector.py lines 126 and 186, then inspect how OnExceptionCheckpoint.dirpath is handled during checkpoint discovery. Reproduce the two consecutive fit calls from the issue and add or update tests so a fit without ckpt_path does not resume from an exception checkpoint and the warnings match that behavior.

Written by the indexing model from the issue text.