[REVIEW] Expose libcudf's label_bins function to cudf

[vyasr]

This PR is a follow-up to #7554 and exposes the feature implemented there via Cython for consumption in cudf's Python API.

[codecov]

Codecov Report

Merging #7724 (f2ddb19) into branch-0.19 (7871e7a) will increase coverage by 0.63%.
The diff coverage is n/a.

❗ Current head f2ddb19 differs from pull request most recent head 251b6c5. Consider uploading reports for the commit 251b6c5 to get more accurate results

@@               Coverage Diff               @@
##           branch-0.19    #7724      +/-   ##
===============================================
+ Coverage        81.86%   82.49%   +0.63%     
===============================================
  Files              101      101              
  Lines            16884    17458     +574     
===============================================
+ Hits             13822    14402     +580     
+ Misses            3062     3056       -6     

Impacted Files	Coverage Δ
python/cudf/cudf/utils/gpu_utils.py	53.65% <0.00%> (-4.88%)	⬇️
python/cudf/cudf/core/column/lists.py	87.68% <0.00%> (-3.72%)	⬇️
python/cudf/cudf/core/column/decimal.py	92.95% <0.00%> (-1.92%)	⬇️
python/cudf/cudf/core/abc.py	87.23% <0.00%> (-1.14%)	⬇️
python/cudf/cudf/core/column/numerical.py	94.83% <0.00%> (-0.20%)	⬇️
python/cudf/cudf/core/column/column.py	87.61% <0.00%> (-0.15%)	⬇️
python/cudf/cudf/utils/utils.py	85.36% <0.00%> (-0.07%)	⬇️
python/cudf/cudf/io/feather.py	100.00% <0.00%> (ø)
python/cudf/cudf/utils/ioutils.py	78.71% <0.00%> (ø)
python/cudf/cudf/comm/serialize.py	0.00% <0.00%> (ø)
... and 45 more

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[kkraus14]

@gpucibot merge