Move code from debugging_connector to trainer.py #10109
Description
Proposed refactoring or deprecation
Move the code from on_init_start in debugging_connector.py to trainer.py and deprecate debugging_connector
https://github.com/PyTorchLightning/pytorch-lightning/blob/c9bc10ce8473a2249ffa4e00972c0c3c1d2641c4/pytorch_lightning/trainer/connectors/debugging_connector.py#L26
Motivation
There is not a lot of code in debugging_connector.py and rather than maintain a separate class to slightly extend the logic in the trainer, we can simplify things by moving the logic to trainer and removing debugging_connector.