Simplified command line tool perf option output

[cesarzc]

This change simplifies the command line tool perf option output to make it easier to be consumed.

A sample of the updated output would be the following:

{
  "OverallCompilation": 3817,
  "OverallCompilation.Build": 1367,
  "OverallCompilation.OutputGeneration": 52,
  "OverallCompilation.OutputGeneration.BinaryGeneration": 6,
  "OverallCompilation.OutputGeneration.SyntaxTreeSerialization": 45,
  "OverallCompilation.ReferenceLoading": 2293,
  "OverallCompilation.RewriteSteps": 49,
  "OverallCompilation.SourcesLoading": 37
}