Add in a utility to run and test CLI model without the CLI

[jlperla]

Maybe something like

def solve_cli_model(Model, args, config_file, default_seed = 123, ):
    sys.argv = ["dummy.py"] + [f"--{key}={val}" for key, val in args.items()]  # hack overwriting  argv

    cli = LightningCLI(
        Model,
        run=False,
        seed_everything_default=default_seed,
        save_config_overwrite=True,        
        parser_kwargs={"default_config_files": [config_file]},
    )
    # Solves the model
    trainer = cli.instantiate_trainer(
        logger=None,
        checkpoint_callback=None,
        callbacks=[],  # not using the early stopping/etc.
    )    
    trainer.fit(cli.model)

    # Calculates the "test" values for it
    trainer.test(cli.model)
    cli.model.eval()  # Turn off training mode, where it calculates gradients for every call.

    return cli.model, cli

Except maybe give a few options with defaults as:

• use_logger = False, turns off the logger if they ask.
• checkpoint_callback = False
• callbacks = False where if False it zeros them out. Otherwise leaves them be.
• test = True, for whe3ther to run the test or not.

Etc.