[REVIEW][FEA] Port nvtx.pyx to use non-legacy libcudf APIs

[millerhooks]

Added nvtx.pyx for libcudf++.

TODO:

• Refactor existing uses of nvtx to use libcudf++

closes #3937

[codecov]

Codecov Report

Merging #4235 into branch-0.13 will increase coverage by 0.01%.
The diff coverage is 100%.

@@              Coverage Diff               @@
##           branch-0.13   #4235      +/-   ##
==============================================
+ Coverage        88.68%   88.7%   +0.01%     
==============================================
  Files               50      50              
  Lines             9800    9851      +51     
==============================================
+ Hits              8691    8738      +47     
- Misses            1109    1113       +4

Impacted Files	Coverage Δ
python/cudf/cudf/core/column/datetime.py	87.5% <ø> (-0.1%)	⬇️
python/cudf/cudf/_libxx/__init__.py	100% <ø> (ø)	⬆️
python/cudf/cudf/core/dataframe.py	89.87% <100%> (+0.01%)	⬆️
python/cudf/cudf/core/column/string.py	86.72% <100%> (ø)	⬆️
python/cudf/cudf/core/series.py	91.42% <100%> (-0.01%)	⬇️
python/cudf/cudf/core/groupby/groupby.py	96.24% <100%> (+0.01%)	⬆️
python/cudf/cudf/core/column/numerical.py	93.86% <100%> (-0.03%)	⬇️
python/dask_cudf/dask_cudf/core.py	72.42% <0%> (-2.58%)	⬇️
python/cudf/cudf/core/index.py	89.11% <0%> (ø)	⬆️
python/dask_cudf/dask_cudf/batcher_sortnet.py
... and 4 more

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[millerhooks]

I realize the if/else is hack. I was having issues getting a dictionary to work properly. Now that this works I'll see if I can't make the dict work.

[kkraus14]

I realize the if/else is hack. I was having issues getting a dictionary to work properly. Now that this works I'll see if I can't make the dict work.

Instead of using a dictionary use a Python Enum and use typecasting to the underlying_type similar to: https://github.com/rapidsai/cudf/blob/branch-0.13/python/cudf/cudf/_libxx/types.pyx