ARROW-6383: [Java] Report outstanding child allocators on close

[pravindra]

• this was happening in debug code, now added in non-debug

[codecov-io]

Codecov Report

Merging #5227 into master will increase coverage by 1.99%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #5227      +/-   ##
==========================================
+ Coverage   87.67%   89.67%   +1.99%     
==========================================
  Files        1025      693     -332     
  Lines      147030   104108   -42922     
  Branches     1437        0    -1437     
==========================================
- Hits       128915    93357   -35558     
+ Misses      17753    10751    -7002     
+ Partials      362        0     -362

Impacted Files	Coverage Δ
cpp/src/gandiva/function_holder_registry.h	75% <0%> (-15%)	⬇️
cpp/src/arrow/filesystem/filesystem.cc	80% <0%> (-6.8%)	⬇️
cpp/src/gandiva/gdv_function_stubs.cc	89.6% <0%> (-4.32%)	⬇️
cpp/src/arrow/json/converter.cc	90.05% <0%> (-1.76%)	⬇️
cpp/src/arrow/json/chunked_builder.cc	79.91% <0%> (-1.68%)	⬇️
cpp/src/arrow/vendored/xxhash/xxhash.c	72.39% <0%> (-1.21%)	⬇️
cpp/src/plasma/thirdparty/ae/ae.c	70.75% <0%> (-0.95%)	⬇️
python/pyarrow/types.pxi	68.04% <0%> (-0.61%)	⬇️
cpp/src/arrow/type.cc	94.02% <0%> (-0.6%)	⬇️
cpp/src/arrow/flight/server.cc	88.28% <0%> (-0.43%)	⬇️
... and 384 more

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[liyafan82]

LGTM.

[pravindra]

thanks for the review @liyafan82