[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_device_quantile_dmatrix.py

@@ -203,7 +203,7 @@ class TestQuantileDMatrix:
         np.testing.assert_equal(h_ret.indices, d_ret.indices)
 
         booster = xgb.train(
-            {"tree_method": "gpu_hist", "predictor": "gpu_predictor"}, dtrain=d_m
+            {"tree_method": "gpu_hist", "gpu_id": "0"}, dtrain=d_m
         )
 
         np.testing.assert_allclose(