Fix lists and structs gtests coded in namespace cudf::test

[davidwendt]

Description

Fixes structs and lists gtests source files coded in namespace cudf::test
These are the only 2 problem files for this in cpp/tests/structs and cpp/tests/lists and so will make those two directories complete.
No function or test has changed just the source code reworked per namespaces.

Reference #11734

Checklist

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

[vuule]

👍

[codecov]

Codecov Report

Base: 88.11% // Head: 88.14% // Increases project coverage by +0.03% 🎉

Coverage data is based on head (ba5abdd) compared to base (5c2150e).
Patch has no changes to coverable lines.

Additional details and impacted files

@@               Coverage Diff                @@
##           branch-22.12   #11956      +/-   ##
================================================
+ Coverage         88.11%   88.14%   +0.03%     
================================================
  Files               133      133              
  Lines             21982    21982              
================================================
+ Hits              19369    19376       +7     
+ Misses             2613     2606       -7     

Impacted Files	Coverage Δ
python/cudf/cudf/core/dataframe.py	93.77% <0.00%> (+0.04%)	⬆️
python/cudf/cudf/core/column/string.py	88.65% <0.00%> (+0.12%)	⬆️
python/cudf/cudf/core/groupby/groupby.py	91.51% <0.00%> (+0.20%)	⬆️
python/cudf/cudf/core/tools/datetimes.py	84.49% <0.00%> (+0.30%)	⬆️
python/cudf/cudf/core/column/lists.py	93.75% <0.00%> (+0.96%)	⬆️
python/strings_udf/strings_udf/__init__.py	86.27% <0.00%> (+1.96%)	⬆️

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[davidwendt]

rerun tests

[davidwendt]

@gpucibot merge