Derive Clone and PartialEq for json DecoderOptions

[alamb]

Which issue does this PR close?

Closes #1580

Rationale for this change

see ticket

What changes are included in this PR?

derive Clone and PartialEq, test

Are there any user-facing changes?

yes

[codecov-commenter]

Codecov Report

Merging #1581 (04bc93e) into master (dbc47e0) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1581      +/-   ##
==========================================
- Coverage   82.87%   82.87%   -0.01%     
==========================================
  Files         193      193              
  Lines       55304    55311       +7     
==========================================
+ Hits        45835    45840       +5     
- Misses       9469     9471       +2     

Impacted Files	Coverage Δ
arrow/src/json/reader.rs	84.52% <100.00%> (+0.03%)	⬆️
arrow/src/datatypes/datatype.rs	66.40% <0.00%> (-0.40%)	⬇️
arrow/src/datatypes/field.rs	54.32% <0.00%> (-0.30%)	⬇️
parquet/src/encodings/encoding.rs	93.37% <0.00%> (-0.19%)	⬇️
arrow/src/ipc/reader.rs	88.61% <0.00%> (ø)
parquet_derive/src/parquet_field.rs	65.98% <0.00%> (ø)
arrow/src/compute/kernels/substring.rs	98.31% <0.00%> (ø)
arrow/src/compute/kernels/cast.rs	95.74% <0.00%> (+<0.01%)	⬆️
parquet/src/column/writer.rs	92.42% <0.00%> (+<0.01%)	⬆️
parquet/src/file/properties.rs	95.76% <0.00%> (+0.01%)	⬆️
... and 1 more

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