Change device_vector to device_uvector for strings_column_view

[davidwendt]

References #7287

This replaces device_vector with device_uvector in strings_column_view functions.
This cascaded to some dependent functions that needed to be updated as well.

[harrism]

I think there's a copy error. Also opportunity to create a useful uvector utility.

[rgsl888prabhu]

Don't have any other concerns apart from what have been already raised.

[harrism]

Can you please put make_std_vector in vector_factories.hpp and make _async and _sync versions to match make_device_uvector?

[davidwendt]

Can you please put make_std_vector in vector_factories.hpp and make _async and _sync versions to match make_device_uvector?

Absolutely. Are you ok with the name?

[rgsl888prabhu]

Minor comment, rest looks good.

[harrism]

Is the async version of make_std_vector safe? Could the temp host array be freed before the copy completes?

[codecov]

Codecov Report

Merging #7798 (f5b7eb2) into branch-0.20 (599f62d) will increase coverage by 0.04%.
The diff coverage is 87.60%.

❗ Current head f5b7eb2 differs from pull request most recent head f5a73a3. Consider uploading reports for the commit f5a73a3 to get more accurate results

@@               Coverage Diff               @@
##           branch-0.20    #7798      +/-   ##
===============================================
+ Coverage        82.30%   82.34%   +0.04%     
===============================================
  Files              101      103       +2     
  Lines            17053    17355     +302     
===============================================
+ Hits             14035    14291     +256     
- Misses            3018     3064      +46     

Impacted Files	Coverage Δ
python/cudf/cudf/utils/dtypes.py	83.44% <46.66%> (-6.45%)	⬇️
python/cudf/cudf/core/groupby/groupby.py	92.25% <78.57%> (-1.21%)	⬇️
python/cudf/cudf/core/column/lists.py	86.95% <80.00%> (-0.27%)	⬇️
python/dask_cudf/dask_cudf/backends.py	89.28% <83.33%> (-0.35%)	⬇️
python/cudf/cudf/core/column/struct.py	96.15% <86.66%> (-3.85%)	⬇️
python/cudf/cudf/core/index.py	92.58% <88.09%> (-0.44%)	⬇️
python/cudf/cudf/core/column/decimal.py	92.92% <91.48%> (-0.92%)	⬇️
python/cudf/cudf/core/column/interval.py	90.69% <92.30%> (+0.07%)	⬆️
python/cudf/cudf/core/column/column.py	87.90% <92.59%> (+0.46%)	⬆️
python/cudf/cudf/core/join/join.py	96.72% <93.75%> (+0.20%)	⬆️
... and 18 more

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[davidwendt]

Is the async version of make_std_vector safe? Could the temp host array be freed before the copy completes?

There should be no temp host array since it is returned.
It should work the same as make_device_uvector_async which returns a device_uvector.
https://godbolt.org/z/PhP7svnn3

[davidwendt]

@gpucibot merge