[REVIEW] Enable workaround to write categorical columns in csv

[galipremsagar]

This PR introduces stopgap solution to write categorical data to csv. In addition, there are also changes to raise error messages to some of the existing issues in CSV reader and writer.

[GPUtester]

Please update the changelog in order to start CI tests.

View the gpuCI docs here.

[codecov]

Codecov Report

Merging #6829 (c097977) into branch-0.17 (e01ab96) will decrease coverage by 0.36%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           branch-0.17    #6829      +/-   ##
===============================================
- Coverage        82.31%   81.94%   -0.37%     
===============================================
  Files               93       96       +3     
  Lines            15358    16142     +784     
===============================================
+ Hits             12642    13228     +586     
- Misses            2716     2914     +198     

Impacted Files	Coverage Δ
python/cudf/cudf/benchmarks/bench_cudf_io.py	30.61% <0.00%> (-12.25%)	⬇️
python/cudf/cudf/io/orc.py	89.39% <0.00%> (-8.23%)	⬇️
python/cudf/cudf/utils/ioutils.py	79.88% <0.00%> (-6.23%)	⬇️
python/dask_cudf/dask_cudf/core.py	73.68% <0.00%> (-0.67%)	⬇️
python/cudf/cudf/core/column/numerical.py	94.50% <0.00%> (-0.49%)	⬇️
python/dask_cudf/dask_cudf/io/parquet.py	91.07% <0.00%> (-0.29%)	⬇️
python/cudf/cudf/core/column/string.py	86.79% <0.00%> (-0.10%)	⬇️
python/cudf/cudf/io/parquet.py	91.66% <0.00%> (-0.07%)	⬇️
python/cudf/cudf/__init__.py	100.00% <0.00%> (ø)
python/cudf/cudf/comm/gpuarrow.py	79.76% <0.00%> (ø)
... and 25 more

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[kkraus14]

LGTM, thanks @galipremsagar

[rgsl888prabhu]

LGTM, just a question regarding test case