[Review] Correct the sampling range when sampling with replacement

[ChrisJar]

This corrects an issue with the sampling range used when replacement=True. Before, it sampled the range 0 through num_rows meaning it could sample num_rows even though it's one position out of bounds. This caused sample to return values not present in the original DataFrame.

I also created exceptions for sampling on empty DataFrames that match pandas, as well as an exception for sampling when axis=1 and replace=True as cudf does not support DataFrames with duplicate columns.

This closes #6532 and #6882

[codecov]

Codecov Report

Merging #6884 (d5212f5) into branch-0.18 (6d1b076) will increase coverage by 1.10%.
The diff coverage is 62.50%.

@@               Coverage Diff               @@
##           branch-0.18    #6884      +/-   ##
===============================================
+ Coverage        82.01%   83.12%   +1.10%     
===============================================
  Files               96       96              
  Lines            16340    17873    +1533     
===============================================
+ Hits             13402    14857    +1455     
- Misses            2938     3016      +78     

Impacted Files	Coverage Δ
python/cudf/cudf/core/frame.py	89.08% <62.50%> (-1.27%)	⬇️
python/dask_cudf/dask_cudf/io/tests/test_csv.py	100.00% <0.00%> (ø)
python/cudf/cudf/core/column/categorical.py	93.62% <0.00%> (+0.29%)	⬆️
python/dask_cudf/dask_cudf/core.py	74.01% <0.00%> (+0.32%)	⬆️
python/cudf/cudf/core/indexing.py	96.35% <0.00%> (+0.72%)	⬆️
python/cudf/cudf/core/series.py	91.98% <0.00%> (+0.88%)	⬆️
python/cudf/cudf/core/column/string.py	87.48% <0.00%> (+0.89%)	⬆️
python/cudf/cudf/core/column/timedelta.py	90.97% <0.00%> (+1.43%)	⬆️
python/dask_cudf/dask_cudf/io/csv.py	96.96% <0.00%> (+1.44%)	⬆️
... and 4 more

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[harrism]

The C++ fix is fine. Just need clarification on the Python exception messages.

[kkraus14]

rerun tests