[BUG] list contains requires passing a device scalar

[beckernick]

In the 2021-04-05 nightly, list.contains currently requires explicitly passing a device scalar. We should create the device scalar under the hood if it's required by the routine.

import cudf
​
df = cudf.DataFrame({"a":[[0,1],[1,2]]})
df.a.list.contains(cudf.Scalar(2)) # works
df.a.list.contains(2)
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-7-9ed499d3bea5> in <module>
      3 df = cudf.DataFrame({"a":[[0,1],[1,2]]})
      4 df.a.list.contains(cudf.Scalar(2)) # works
----> 5 df.a.list.contains(2)

/raid/nicholasb/miniconda3/envs/rapids-gpubdb-20210405/lib/python3.7/site-packages/cudf/core/column/lists.py in contains(self, search_key)
    240         try:
    241             res = self._return_or_inplace(
--> 242                 contains_scalar(self._column, search_key.device_value)
    243             )
    244         except RuntimeError as e:

AttributeError: 'int' object has no attribute 'device_value'

conda list | grep "rapids\|numpy\|cupy"
# packages in environment at /raid/nicholasb/miniconda3/envs/rapids-gpubdb-20210405:
cudf                      0.19.0a210405   cuda_10.2_py37_g73638bbfea_343    rapidsai-nightly
cuml                      0.19.0a210405   cuda10.2_py37_g4bf0ba4da_152    rapidsai-nightly
cupy                      8.6.0            py37h7fc54ca_0    conda-forge
dask-cuda                 0.19.0a210405           py37_46    rapidsai-nightly
dask-cudf                 0.19.0a210405   py37_g73638bbfea_343    rapidsai-nightly
libcudf                   0.19.0a210405   cuda10.2_g73638bbfea_343    rapidsai-nightly
libcuml                   0.19.0a210405   cuda10.2_g4bf0ba4da_152    rapidsai-nightly
libcumlprims              0.19.0a210402   cuda10.2_g8859156_34    rapidsai-nightly
librmm                    0.19.0a210405   cuda10.2_gbefea87_53    rapidsai-nightly
numpy                     1.19.5           py37haa41c4c_1    conda-forge
rmm                       0.19.0a210405   cuda_10.2_py37_gbefea87_53    rapidsai-nightly
ucx                       1.9.0+gcd9efd3       cuda10.2_0    rapidsai-nightly
ucx-proc                  1.0.0                       gpu    rapidsai-nightly
ucx-py                    0.19.0a210405   py37_gcd9efd3_47    rapidsai-nightly