Convert benchmarks to use device_uvector

[harrism]

Converts all remaining benchmark code to use device_uvector instead of device_vector.

Contributes to #7287

[codecov]

Codecov Report

Merging #8208 (b963929) into branch-0.20 (51336df) will decrease coverage by 0.00%.
The diff coverage is n/a.

❗ Current head b963929 differs from pull request most recent head 1c47010. Consider uploading reports for the commit 1c47010 to get more accurate results

@@               Coverage Diff               @@
##           branch-0.20    #8208      +/-   ##
===============================================
- Coverage        82.88%   82.88%   -0.01%     
===============================================
  Files              103      104       +1     
  Lines            17668    17904     +236     
===============================================
+ Hits             14645    14839     +194     
- Misses            3023     3065      +42     

Impacted Files	Coverage Δ
python/cudf/cudf/core/tools/datetimes.py	80.42% <0.00%> (-4.11%)	⬇️
python/cudf/cudf/core/abc.py	87.50% <0.00%> (-3.99%)	⬇️
python/cudf/cudf/core/column/decimal.py	90.20% <0.00%> (-2.72%)	⬇️
python/cudf/cudf/core/column/datetime.py	88.03% <0.00%> (-1.88%)	⬇️
python/cudf/cudf/core/column/struct.py	94.73% <0.00%> (-1.56%)	⬇️
python/cudf/cudf/utils/dtypes.py	82.20% <0.00%> (-1.24%)	⬇️
python/dask_cudf/dask_cudf/groupby.py	91.28% <0.00%> (-0.88%)	⬇️
python/cudf/cudf/core/series.py	91.17% <0.00%> (-0.56%)	⬇️
python/cudf/cudf/core/index.py	92.52% <0.00%> (-0.55%)	⬇️
python/cudf/cudf/core/column/column.py	88.20% <0.00%> (-0.44%)	⬇️
... and 30 more

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[davidwendt]

Looks good. Missing a couple of copyright updates.

[harrism]

@gpucibot merge