[REVIEW] Add support for array-like inputs in cudf.get_dummies

[galipremsagar]

FIxes: #7031

This PR introduces array-like inputs support in cudf.get_dummies. I think in near future we will have to deprecate and adapt new name for get_dummies: pandas-dev/pandas#35724

[codecov]

Codecov Report

Merging #7181 (de61f25) into branch-0.18 (8860baf) will increase coverage by 0.07%.
The diff coverage is 89.01%.

@@               Coverage Diff               @@
##           branch-0.18    #7181      +/-   ##
===============================================
+ Coverage        82.09%   82.16%   +0.07%     
===============================================
  Files               97       97              
  Lines            16474    16559      +85     
===============================================
+ Hits             13524    13606      +82     
- Misses            2950     2953       +3     

Impacted Files	Coverage Δ
python/cudf/cudf/_lib/__init__.py	100.00% <ø> (ø)
python/cudf/cudf/core/column/lists.py	91.66% <ø> (-0.09%)	⬇️
python/cudf/cudf/utils/ioutils.py	78.71% <ø> (ø)
python/cudf/cudf/core/dataframe.py	90.71% <50.00%> (+<0.01%)	⬆️
python/cudf/cudf/io/orc.py	86.89% <63.63%> (-1.51%)	⬇️
python/cudf/cudf/core/dtypes.py	89.50% <66.66%> (-0.88%)	⬇️
python/cudf/cudf/core/series.py	91.10% <80.00%> (-0.06%)	⬇️
python/cudf/cudf/core/column/numerical.py	94.08% <83.33%> (-0.33%)	⬇️
python/cudf/cudf/io/csv.py	91.66% <86.66%> (-1.67%)	⬇️
python/cudf/cudf/core/frame.py	89.90% <88.88%> (-0.08%)	⬇️
... and 7 more

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[kkraus14]

@gpucibot merge