Add coverage for string UDF tests. (#11891)

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.

Authors:
  - Vyas Ramasubramani (https://github.com/vyasr)

Approvers:
  - GALI PREM SAGAR (https://github.com/galipremsagar)
  - https://github.com/brandon-b-miller
  - Jake Awe (https://github.com/AyodeAwe)

URL: #11891

ci/gpu/build.sh

@@ -294,7 +294,7 @@ elif [ ${STRINGS_UDF_PYTEST_RETCODE} -ne 0 ]; then
 else
     cd "$WORKSPACE/python/cudf/cudf"
     gpuci_logger "Python py.test retest cuDF UDFs"
-    py.test tests/test_udf_masked_ops.py -n 8 --cache-clear
+    py.test -n 8 --cache-clear --basetemp="$WORKSPACE/cudf-cuda-strings-udf-tmp" --ignore="$WORKSPACE/python/cudf/cudf/benchmarks" --junitxml="$WORKSPACE/junit-cudf-strings-udf.xml" -v --cov-config="$WORKSPACE/python/cudf/.coveragerc" --cov=cudf --cov-report=xml:"$WORKSPACE/python/cudf/cudf-strings-udf-coverage.xml" --cov-report term --dist=loadscope tests
 fi
 
 # Run benchmarks with both cudf and pandas to ensure compatibility is maintained.

codecov.yml

@@ -2,7 +2,7 @@
 coverage:
   status:
     project: off
-    patch: on
+    patch:
       default:
         target: auto
         threshold: 0%