Use a different schema for each RecordBatch in python getAsArrow

[benjaminwinger]

Fixes #2037.

I also bumped the version of pyarrow used in CI so that the new memory release check that was catching this issue gets used in CI.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.01% 🎉

Comparison is base (fe850a7) 90.22% compared to head (6cc9364) 90.24%.
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2055      +/-   ##
==========================================
+ Coverage   90.22%   90.24%   +0.01%     
==========================================
  Files         950      950              
  Lines       33776    33779       +3     
==========================================
+ Hits        30476    30484       +8     
+ Misses       3300     3295       -5     

Files Changed	Coverage Δ
tools/python_api/src_cpp/include/py_query_result.h	100.00% <ø> (ø)
tools/python_api/src_cpp/py_query_result.cpp	96.15% <100.00%> (-0.05%)	⬇️

... and 17 files with indirect coverage changes

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