Revert "Java API change for supporting structs (#7730)"

[razajafri]

This reverts commit 3327f7b.

We have to revert this because the dependent project is broken and my system is in a broken state.

[rongou]

@gpucibot merge

[codecov]

Codecov Report

Merging #7987 (a7fb3e2) into branch-0.20 (51336df) will increase coverage by 0.01%.
The diff coverage is 87.77%.

❗ Current head a7fb3e2 differs from pull request most recent head 5977b1d. Consider uploading reports for the commit 5977b1d to get more accurate results

@@               Coverage Diff               @@
##           branch-0.20    #7987      +/-   ##
===============================================
+ Coverage        82.88%   82.90%   +0.01%     
===============================================
  Files              103      103              
  Lines            17668    17655      -13     
===============================================
- Hits             14645    14637       -8     
+ Misses            3023     3018       -5     

Impacted Files	Coverage Δ
python/cudf/cudf/core/column/__init__.py	100.00% <ø> (ø)
python/cudf/cudf/utils/cudautils.py	57.75% <25.00%> (ø)
python/cudf/cudf/core/column/column.py	88.64% <71.42%> (ø)
python/cudf/cudf/core/column/numerical.py	94.43% <72.72%> (ø)
python/cudf/cudf/core/dataframe.py	90.87% <83.33%> (+0.01%)	⬆️
python/cudf/cudf/utils/utils.py	89.53% <91.66%> (+0.02%)	⬆️
python/cudf/cudf/core/column/datetime.py	89.91% <100.00%> (ø)
python/cudf/cudf/core/column/timedelta.py	88.66% <100.00%> (ø)
python/cudf/cudf/core/groupby/groupby.py	92.28% <100.00%> (+0.83%)	⬆️
python/cudf/cudf/core/index.py	93.07% <100.00%> (ø)
... and 15 more

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[razajafri]

@gpucibot merge

[razajafri]

@gpucibot merge

[mythrocks]

Merged, at last! I wonder why it took that long.