Add libcudf strings examples

[davidwendt]

Description

Creates example for calling libcudf APIs for strings processing.
This also includes examples of building custom kernels for modifying libcudf strings columns.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[codecov]

Codecov Report

Base: 87.40% // Head: 86.85% // Decreases project coverage by -0.55% ⚠️

Coverage data is based on head (ad65d40) compared to base (f72c4ce).
Patch coverage: 86.52% of modified lines in pull request are covered.

❗ Current head ad65d40 differs from pull request most recent head d95708e. Consider uploading reports for the commit d95708e to get more accurate results

Additional details and impacted files

@@               Coverage Diff                @@
##           branch-22.12   #11849      +/-   ##
================================================
- Coverage         87.40%   86.85%   -0.56%     
================================================
  Files               133      133              
  Lines             21833    21881      +48     
================================================
- Hits              19084    19005      -79     
- Misses             2749     2876     +127     

Impacted Files	Coverage Δ
python/cudf/cudf/core/udf/__init__.py	50.00% <ø> (ø)
python/cudf/cudf/io/orc.py	92.94% <ø> (-0.09%)	⬇️
...thon/dask_cudf/dask_cudf/tests/test_distributed.py	18.86% <ø> (+4.94%)	⬆️
python/cudf/cudf/core/_base_index.py	82.20% <43.75%> (-3.35%)	⬇️
python/cudf/cudf/io/text.py	91.66% <66.66%> (-8.34%)	⬇️
python/strings_udf/strings_udf/__init__.py	84.31% <76.00%> (-12.57%)	⬇️
python/cudf/cudf/core/index.py	92.91% <95.16%> (+0.28%)	⬆️
python/cudf/cudf/__init__.py	90.69% <100.00%> (ø)
python/cudf/cudf/core/column/categorical.py	89.34% <100.00%> (ø)
python/cudf/cudf/core/groupby/groupby.py	91.30% <100.00%> (+0.08%)	⬆️
... and 16 more

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[bdice]

I reviewed the blog post as well, so this code was quick to review. Nice example!

[nvdbaranec]

Most of these comments are along the line of : I'm assuming this is also partially useful as a cuda explainer. If the intended audience here is more advanced, they may not be useful.

[msadang]

LGTM

[davidwendt]

@gpucibot merge