[FEA] Improved error message when calling query() on expresions involving columns of string values

[rlratzel]

DataFrame.query() calls using expressions that involve columns of string values are not supported in cuDF. Adding support for this would be ideal, but given that strings are not fully supported for a variety of reasons, a better error message would be the next best improvement.
As an example, in pandas the following works as expected:

>>> DF4.query("type_name=='merchants' and merchant_size>80 and merchant_location==44145") # pandas version
   vertex  type_name  merchant_location  merchant_size  distro_size  user_location  vertical
2      21  merchants            44145.0           83.0          NaN            NaN       NaN

However, the same code using cudf produces the following:

>>> DF4.query("type_name=='merchants' and merchant_size>80 and merchant_location==44145") # cudf version
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/conda/envs/rapids/lib/python3.8/site-packages/cudf/core/dataframe.py", line 3915, in query
    boolmask = queryutils.query_execute(self, expr, callenv)
  File "/opt/conda/envs/rapids/lib/python3.8/site-packages/cudf/utils/queryutils.py", line 220, in query_execute
    colarrays = [
  File "/opt/conda/envs/rapids/lib/python3.8/site-packages/cudf/utils/queryutils.py", line 221, in <listcomp>
    cudf.core.dataframe.extract_col(df, col).data_array_view
  File "/opt/conda/envs/rapids/lib/python3.8/site-packages/cudf/core/column/string.py", line 5179, in data_array_view
    raise ValueError("Cannot get an array view of a StringColumn")
ValueError: Cannot get an array view of a StringColumn

Perhaps raising TypeError(f"query expression including string column {col} is not supported") or something similar might be better.

NOTE: for those interested, the proposed workaround for the above example is:

DF4[DF4["type_name"]=='merchants'].query(merchant_size>80 and merchant_location==44145")

cc @vyasr @brandon-b-miller

[vyasr]

For context, supporting the query itself requires addressing #9639.