Avoid overflow for fixed_point cudf::cast and performance optimization

[codereport]

This resolves #9000.

When using cudf::cast for a wider decimal type to a narrower decimal type, you can overflow. This PR modifies the code path for this specific use case so that the "rescale" happens for the type cast. A small perf improvement was added when you have identical scales to avoid rescaling.

CI depends on #9766

[codecov]

Codecov Report

Merging #9772 (1291e67) into branch-22.02 (967a333) will decrease coverage by 0.01%.
The diff coverage is 9.24%.

❗ Current head 1291e67 differs from pull request most recent head 3c083ab. Consider uploading reports for the commit 3c083ab to get more accurate results

@@               Coverage Diff                @@
##           branch-22.02    #9772      +/-   ##
================================================
- Coverage         10.49%   10.47%   -0.02%     
================================================
  Files               119      119              
  Lines             20305    20368      +63     
================================================
+ Hits               2130     2133       +3     
- Misses            18175    18235      +60     

Impacted Files	Coverage Δ
python/cudf/cudf/__init__.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/column/column.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/column/string.py	0.00% <ø> (ø)
python/cudf/cudf/core/frame.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/groupby/groupby.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/index.py	0.00% <ø> (ø)
python/cudf/cudf/core/indexed_frame.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/multiindex.py	0.00% <0.00%> (ø)
python/cudf/cudf/utils/utils.py	0.00% <0.00%> (ø)
python/dask_cudf/dask_cudf/io/csv.py	96.00% <100.00%> (+0.10%)	⬆️
... and 1 more

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[codereport]

@gpucibot merge