Extract dask and spark test into distributed test. (#8395)

- Move test files.
- Run spark and dask separately to prevent conflicts.
- Gather common code into the testing module.

tests/test_distributed/test_gpu_with_spark/test_data.py

@@ -0,0 +1,16 @@
+import pytest
+
+from xgboost import testing as tm
+
+pytestmark = pytest.mark.skipif(**tm.no_spark())
+
+from ..test_with_spark.test_data import run_dmatrix_ctor
+
+
+@pytest.mark.skipif(**tm.no_cudf())
+@pytest.mark.parametrize(
+    "is_feature_cols,is_qdm",
+    [(True, True), (True, False), (False, True), (False, False)],
+)
+def test_dmatrix_ctor(is_feature_cols: bool, is_qdm: bool) -> None:
+    run_dmatrix_ctor(is_feature_cols, is_qdm, on_gpu=True)