Add coverage for string UDF tests.

[vyasr]

Description

Many PRs are currently showing Codecov patch status check failures that appear to be the result of not uploading coverage reports for the string UDF tests. This PR should enable the missing coverage and ensure that we are actually measuring coverage of these code paths.

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: 88.10% // Increases project coverage by +0.69% 🎉

Coverage data is based on head (b176763) compared to base (f72c4ce).
Patch coverage: 84.03% of modified lines in pull request are covered.

❗ Current head b176763 differs from pull request most recent head 3f41853. Consider uploading reports for the commit 3f41853 to get more accurate results

Additional details and impacted files

@@               Coverage Diff                @@
##           branch-22.12   #11891      +/-   ##
================================================
+ Coverage         87.40%   88.10%   +0.69%     
================================================
  Files               133      133              
  Lines             21833    21864      +31     
================================================
+ Hits              19084    19263     +179     
+ Misses             2749     2601     -148     

Impacted Files	Coverage Δ
python/cudf/cudf/core/udf/__init__.py	97.05% <ø> (+47.05%)	⬆️
python/cudf/cudf/io/orc.py	92.94% <ø> (-0.09%)	⬇️
python/cudf/cudf/utils/ioutils.py	79.47% <ø> (ø)
...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% <95.08%> (+0.27%)	⬆️
python/cudf/cudf/__init__.py	90.69% <100.00%> (ø)
python/cudf/cudf/core/column/categorical.py	89.34% <100.00%> (ø)
... and 12 more

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[vyasr]

Codecov is consistently computing the same incorrect merge base for all PRs (f72c4ce). Now investigating why.

[brandon-b-miller]

Thanks for catching this!

[galipremsagar]

@gpucibot merge