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ARROW-11189: [Developer] support benchmark diff between JSONs

Enables diffing two cached JSON benchmark results. Also groups regressions and non-regressions for easier inspection:

```shell-session
$ export FILTERS="--benchmark-filter=value-parsing --suite-filter=IntegerFormatting"
$ archery benchmark run $FILTERS --output=baseline.json
$ git checkout $BRANCH
$ archery benchmark run $FILTERS --output=contender.json
$ archery benchmark diff contender.json baseline.json
---------------------------------------------------------------------------------------
Non-regressions: (1)
---------------------------------------------------------------------------------------
                   benchmark            baseline           contender  change % counters
 IntegerFormatting<Int8Type>  106.163m items/sec  108.091m items/sec     1.816       {}

-----------------------------------------------------------------------------------------
Regressions: (9)
-----------------------------------------------------------------------------------------
                     benchmark            baseline           contender  change % counters
  IntegerFormatting<UInt8Type>  112.739m items/sec  102.576m items/sec    -9.015       {}
 IntegerFormatting<UInt32Type>   61.029m items/sec   54.603m items/sec   -10.530       {}
  IntegerFormatting<Int16Type>   86.396m items/sec   74.601m items/sec   -13.653       {}
  IntegerFormatting<Int32Type>   61.305m items/sec   51.841m items/sec   -15.437       {}
 IntegerFormatting<UInt16Type>   88.665m items/sec   74.442m items/sec   -16.041       {}
 IntegerFormatting<UInt64Type>   34.248m items/sec   27.239m items/sec   -20.464       {}
  IntegerFormatting<Int64Type>   38.401m items/sec   27.475m items/sec   -28.451       {}
   FloatFormatting<DoubleType>    5.642m items/sec    3.614m items/sec   -35.939       {}
    FloatFormatting<FloatType>    5.823m items/sec    3.608m items/sec   -38.038       {}
```

Closes #9140 from bkietz/11189-Achery-benchmark-diff-can

Lead-authored-by: Benjamin Kietzman <bengilgit@gmail.com>
Co-authored-by: Antoine Pitrou <antoine@python.org>
Signed-off-by: Antoine Pitrou <antoine@python.org>