[REVIEW] Materialize RangeIndex when index=True in parquet writer

[galipremsagar]

Resolves: #6873

This PR enables support to materialize a RangeIndex when index=True. Didn't add any tests as we already test for this in test_parquet_index but we were having the tests wrong due to a typo which was writing to the same file both pandas & cudf dataframes. This test is now fixed in this PR.

[kkraus14]

@gpucibot merge

[codecov]

Codecov Report

Merging #7711 (5072e6b) into branch-0.19 (7871e7a) will increase coverage by 0.64%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           branch-0.19    #7711      +/-   ##
===============================================
+ Coverage        81.86%   82.50%   +0.64%     
===============================================
  Files              101      101              
  Lines            16884    17441     +557     
===============================================
+ Hits             13822    14390     +568     
+ Misses            3062     3051      -11     

Impacted Files	Coverage Δ
python/cudf/cudf/core/buffer.py	84.21% <ø> (+4.96%)	⬆️
python/cudf/cudf/core/column/categorical.py	91.97% <ø> (+0.58%)	⬆️
python/cudf/cudf/core/column/column.py	87.61% <ø> (-0.15%)	⬇️
python/cudf/cudf/core/column/datetime.py	89.63% <ø> (+0.54%)	⬆️
python/cudf/cudf/core/column/decimal.py	92.75% <ø> (-2.12%)	⬇️
python/cudf/cudf/core/column/lists.py	90.00% <ø> (-1.40%)	⬇️
python/cudf/cudf/core/column/numerical.py	94.83% <ø> (-0.20%)	⬇️
python/cudf/cudf/core/column/string.py	86.79% <ø> (+0.30%)	⬆️
python/cudf/cudf/core/column/timedelta.py	88.57% <ø> (+0.33%)	⬆️
python/cudf/cudf/core/column_accessor.py	96.13% <ø> (+0.82%)	⬆️
... and 58 more

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