Add DecimalType support in new_null_array

[yjshen]

Which issue does this PR close?

N/A.

Rationale for this change

Support creation of all null decimal array.

What changes are included in this PR?

Are there any user-facing changes?

[codecov-commenter]

Codecov Report

Merging #1659 (194ea02) into master (884de44) will decrease coverage by 0.02%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #1659      +/-   ##
==========================================
- Coverage   83.08%   83.06%   -0.03%     
==========================================
  Files         193      193              
  Lines       55775    55788      +13     
==========================================
- Hits        46341    46340       -1     
- Misses       9434     9448      +14     

Impacted Files	Coverage Δ
arrow/src/array/array.rs	89.67% <0.00%> (-3.04%)	⬇️
parquet/src/encodings/encoding.rs	93.37% <0.00%> (-0.19%)	⬇️
parquet_derive/src/parquet_field.rs	66.21% <0.00%> (ø)

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[alamb]

Thanks @yjshen