Clean up release after cloning source structs

[viirya]

Which issue does this PR close?

Closes #1425.

Rationale for this change

What changes are included in this PR?

This is an alternative proposal for #1425.

Are there any user-facing changes?

[codecov-commenter]

Codecov Report

Merging #1436 (df126d0) into master (729934c) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head df126d0 differs from pull request most recent head 2fe4ae1. Consider uploading reports for the commit 2fe4ae1 to get more accurate results

@@           Coverage Diff           @@
##           master    #1436   +/-   ##
=======================================
  Coverage   82.67%   82.68%           
=======================================
  Files         185      185           
  Lines       53822    53824    +2     
=======================================
+ Hits        44500    44506    +6     
+ Misses       9322     9318    -4     

Impacted Files	Coverage Δ
arrow/src/ffi.rs	85.84% <100.00%> (+0.06%)	⬆️
arrow/src/array/transform/mod.rs	86.43% <0.00%> (+0.11%)	⬆️
parquet_derive/src/parquet_field.rs	66.21% <0.00%> (+0.22%)	⬆️
arrow/src/datatypes/field.rs	54.10% <0.00%> (+0.30%)	⬆️
arrow/src/datatypes/datatype.rs	66.80% <0.00%> (+0.39%)	⬆️

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[viirya]

cc @sunchao @alamb @wangfenjin