Remove cudf._lib.round in favor of inlining pylibcudf (#17430)

Contributes to #17317

Authors:
  - Matthew Roeschke (https://github.com/mroeschke)

Approvers:
  - Matthew Murray (https://github.com/Matt711)

URL: #17430

python/cudf/cudf/_lib/CMakeLists.txt

@@ -21,7 +21,6 @@ set(cython_sources
     orc.pyx
     parquet.pyx
     reduce.pyx
-    round.pyx
     scalar.pyx
     sort.pyx
     stream_compaction.pyx

python/cudf/cudf/_lib/__init__.py

@@ -10,7 +10,6 @@
     orc,
     parquet,
     reduce,
-    round,
     sort,
     stream_compaction,
     string_casting,

python/cudf/cudf/core/column/numerical_base.py

@@ -3,7 +3,7 @@
 
 from __future__ import annotations
 
-from typing import TYPE_CHECKING, cast
+from typing import TYPE_CHECKING, Literal, cast
 
 import numpy as np
 
@@ -246,12 +246,21 @@ def corr(self, other: NumericalBaseColumn) -> float:
         return cov / lhs_std / rhs_std
 
     def round(
-        self, decimals: int = 0, how: str = "half_even"
+        self,
+        decimals: int = 0,
+        how: Literal["half_even", "half_up"] = "half_even",
     ) -> NumericalBaseColumn:
         if not cudf.api.types.is_integer(decimals):
-            raise TypeError("Values in decimals must be integers")
-        """Round the values in the Column to the given number of decimals."""
-        return libcudf.round.round(self, decimal_places=decimals, how=how)
+            raise TypeError("Argument 'decimals' must an integer")
+        if how not in {"half_even", "half_up"}:
+            raise ValueError(f"{how=} must be either 'half_even' or 'half_up'")
+        plc_how = plc.round.RoundingMethod[how.upper()]
+        with acquire_spill_lock():
+            return type(self).from_pylibcudf(  # type: ignore[return-value]
+                plc.round.round(
+                    self.to_pylibcudf(mode="read"), decimals, plc_how
+                )
+            )
 
     def _scan(self, op: str) -> ColumnBase:
         return libcudf.reduce.scan(