Register read_parquet and read_csv with dask-expr (#16535)

After dask/dask-expr#1114, Dask cuDF must register specific `read_parquet` and `read_csv` functions to be used when query-planning is enabled (the default).

**This PR is required for CI to pass with dask>2024.8.0**

**NOTE**: It probably doesn't make sense to add specific tests for this change. Once the 2014.7.1 dask pin is removed, all `dask_cudf` tests using `read_parquet` and  `read_csv` will fail without this change...

Authors:
  - Richard (Rick) Zamora (https://github.com/rjzamora)

Approvers:
  - Mads R. B. Kristensen (https://github.com/madsbk)
  - Benjamin Zaitlen (https://github.com/quasiben)

URL: #16535

python/dask_cudf/dask_cudf/backends.py

@@ -667,6 +667,41 @@ def from_dict(
             constructor=constructor,
         )
 
+    @staticmethod
+    def read_parquet(*args, engine=None, **kwargs):
+        import dask_expr as dx
+
+        from dask_cudf.io.parquet import CudfEngine
+
+        return _default_backend(
+            dx.read_parquet, *args, engine=CudfEngine, **kwargs
+        )
+
+    @staticmethod
+    def read_csv(
+        path,
+        *args,
+        header="infer",
+        dtype_backend=None,
+        storage_options=None,
+        **kwargs,
+    ):
+        import dask_expr as dx
+        from fsspec.utils import stringify_path
+
+        if not isinstance(path, str):
+            path = stringify_path(path)
+        return dx.new_collection(
+            dx.io.csv.ReadCSV(
+                path,
+                dtype_backend=dtype_backend,
+                storage_options=storage_options,
+                kwargs=kwargs,
+                header=header,
+                dataframe_backend="cudf",
+            )
+        )
+
     @staticmethod
     def read_json(*args, **kwargs):
         from dask_cudf.io.json import read_json as read_json_impl