[breaking] Remove the predictor param, allow fallback to prediction using DMatrix. (#9129)

- A `DeviceOrd` struct is implemented to indicate the device. It will eventually replace the `gpu_id` parameter.
- The `predictor` parameter is removed.
- Fallback to `DMatrix` when `inplace_predict` is not available.
- The heuristic for choosing a predictor is only used during training.

tests/python-gpu/test_gpu_updaters.py

@@ -260,7 +260,6 @@ class TestGPUUpdaters:
                 "seed": 66,
                 "subsample": 0.5,
                 "gamma": 0.2,
-                "predictor": "auto",
                 "eval_metric": "auc",
             },
             num_boost_round=150,