Add subtract_scalar kernel

[viirya]

Which issue does this PR close?

Closes #1153.

Rationale for this change

What changes are included in this PR?

Are there any user-facing changes?

[codecov-commenter]

Codecov Report

Merging #1152 (506e730) into master (719096b) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1152      +/-   ##
==========================================
+ Coverage   82.55%   82.56%   +0.01%     
==========================================
  Files         169      169              
  Lines       50456    50512      +56     
==========================================
+ Hits        41655    41707      +52     
- Misses       8801     8805       +4     

Impacted Files	Coverage Δ
arrow/src/compute/kernels/arithmetic.rs	84.64% <100.00%> (+0.50%)	⬆️
arrow/src/datatypes/field.rs	53.79% <0.00%> (-0.31%)	⬇️
arrow/src/array/transform/mod.rs	85.43% <0.00%> (-0.27%)	⬇️
parquet_derive/src/parquet_field.rs	66.21% <0.00%> (-0.23%)	⬇️
parquet/src/compression.rs	88.59% <0.00%> (ø)
parquet/src/arrow/arrow_writer.rs	98.07% <0.00%> (ø)
arrow/src/compute/kernels/comparison.rs	91.96% <0.00%> (ø)
arrow/src/array/array_string.rs	97.40% <0.00%> (+0.32%)	⬆️
arrow/src/util/test_util.rs	92.04% <0.00%> (+1.13%)	⬆️

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[viirya]

I will rebase this to simd_unary_math_op once #1151 gets merged.

[alamb]

it should be good to go now

[liukun4515]

LGTM
thanks

[alamb]

Thanks @viirya

[viirya]

Thanks @alamb !