Move Python testing utilities into xgboost module. (#8379)

- Add typehints.
- Fixes for pylint.

Co-authored-by: Hyunsu Philip Cho <chohyu01@cs.washington.edu>

tests/python-gpu/test_large_input.py

@@ -1,23 +1,23 @@
-import numpy as np
-import xgboost as xgb
-import cupy as cp
-import time
-import pytest
-
-
-# Test for integer overflow or out of memory exceptions
-def test_large_input():
-    available_bytes, _ = cp.cuda.runtime.memGetInfo()
-    # 15 GB
-    required_bytes = 1.5e+10
-    if available_bytes < required_bytes:
-        pytest.skip("Not enough memory on this device")
-    n = 1000
-    m = ((1 << 31) + n - 1) // n
-    assert (np.log2(m * n) > 31)
-    X = cp.ones((m, n), dtype=np.float32)
-    y = cp.ones(m)
-    dmat = xgb.DeviceQuantileDMatrix(X, y)
-    booster = xgb.train({"tree_method": "gpu_hist", "max_depth": 1}, dmat, 1)
-    del y
-    booster.inplace_predict(X)
+import cupy as cp
+import numpy as np
+import pytest
+
+import xgboost as xgb
+
+
+# Test for integer overflow or out of memory exceptions
+def test_large_input():
+    available_bytes, _ = cp.cuda.runtime.memGetInfo()
+    # 15 GB
+    required_bytes = 1.5e+10
+    if available_bytes < required_bytes:
+        pytest.skip("Not enough memory on this device")
+    n = 1000
+    m = ((1 << 31) + n - 1) // n
+    assert (np.log2(m * n) > 31)
+    X = cp.ones((m, n), dtype=np.float32)
+    y = cp.ones(m)
+    dmat = xgb.DeviceQuantileDMatrix(X, y)
+    booster = xgb.train({"tree_method": "gpu_hist", "max_depth": 1}, dmat, 1)
+    del y
+    booster.inplace_predict(X)