Add backend for percentile_lookup dispatch (#9118)

This PR adds backend for `percentile_lookup` dispatch in `dask_cudf`, related dask upstream changes were done in dask/dask#8083

Authors:
  - GALI PREM SAGAR (https://github.com/galipremsagar)

Approvers:
  - https://github.com/jakirkham

URL: #9118

python/dask_cudf/dask_cudf/backends.py

@@ -259,9 +259,14 @@ def is_categorical_dtype_cudf(obj):
 
 
 try:
-    from dask.dataframe.dispatch import percentile_dispatch
+    try:
+        from dask.array.dispatch import percentile_lookup
+    except ImportError:
+        from dask.dataframe.dispatch import (
+            percentile_dispatch as percentile_lookup,
+        )
 
-    @percentile_dispatch.register((cudf.Series, cp.ndarray, cudf.Index))
+    @percentile_lookup.register((cudf.Series, cp.ndarray, cudf.Index))
     def percentile_cudf(a, q, interpolation="linear"):
         # Cudf dispatch to the equivalent of `np.percentile`:
         # https://numpy.org/doc/stable/reference/generated/numpy.percentile.html