ARROW-6005: [C++] extend GetRecordBatchReader test to cover reading a single row group

[hatemhelal]

This adds a basic unittest for row group selection with the GetRecordBatchReader API.

[codecov-io]

Codecov Report

Merging #5012 into master will increase coverage by 1.85%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #5012      +/-   ##
==========================================
+ Coverage   87.32%   89.18%   +1.85%     
==========================================
  Files         895      727     -168     
  Lines      119946   102952   -16994     
  Branches     1418        0    -1418     
==========================================
- Hits       104748    91821   -12927     
+ Misses      14836    11131    -3705     
+ Partials      362        0     -362

Impacted Files	Coverage Δ
cpp/src/parquet/arrow/arrow-reader-writer-test.cc	93.73% <100%> (+0.05%)	⬆️
cpp/src/arrow/array-binary-test.cc	100% <0%> (ø)	⬆️
cpp/src/arrow/array/builder_base.h	92.5% <0%> (ø)	⬆️
go/arrow/ipc/writer.go
go/arrow/math/uint64_amd64.go
go/arrow/memory/memory_avx2_amd64.go
rust/datafusion/src/execution/filter.rs
rust/arrow/src/csv/writer.rs
rust/datafusion/src/bin/main.rs
go/arrow/ipc/file_reader.go
... and 461 more

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[wesm]

+1