Rewrite cudf internals using pylibcudf groupby (#14946)

This PR builds on #14945 to use pylibcudf's groupby in cudf's internals. It should not be merged until after that PR.

Authors:
  - Vyas Ramasubramani (https://github.com/vyasr)

Approvers:
  - Ashwin Srinath (https://github.com/shwina)

URL: #14946

python/cudf/cudf/_lib/aggregation.pxd

@@ -1,7 +1,8 @@
-# Copyright (c) 2020-2022, NVIDIA CORPORATION.
+# Copyright (c) 2020-2024, NVIDIA CORPORATION.
 
 from libcpp.memory cimport unique_ptr
 
+from cudf._lib cimport pylibcudf
 from cudf._lib.cpp.aggregation cimport (
     groupby_aggregation,
     groupby_scan_aggregation,
@@ -15,10 +16,7 @@ cdef class RollingAggregation:
     cdef unique_ptr[rolling_aggregation] c_obj
 
 cdef class GroupbyAggregation:
-    cdef unique_ptr[groupby_aggregation] c_obj
-
-cdef class GroupbyScanAggregation:
-    cdef unique_ptr[groupby_scan_aggregation] c_obj
+    cdef pylibcudf.aggregation.Aggregation c_obj
 
 cdef class ReduceAggregation:
     cdef unique_ptr[reduce_aggregation] c_obj
@@ -28,6 +26,5 @@ cdef class ScanAggregation:
 
 cdef RollingAggregation make_rolling_aggregation(op, kwargs=*)
 cdef GroupbyAggregation make_groupby_aggregation(op, kwargs=*)
-cdef GroupbyScanAggregation make_groupby_scan_aggregation(op, kwargs=*)
 cdef ReduceAggregation make_reduce_aggregation(op, kwargs=*)
 cdef ScanAggregation make_scan_aggregation(op, kwargs=*)