Make regreph a console app with two commands

`bin/regreph` is now a `symfony/console` application with two commands:
 - bench - bench a library based on a test file
 - regreph - bench the working dir and a past refspec of a library and compare the results

The regreph command is no longer using the bench command through the shell.
Instead it is using the common Regreph\Bench classes to perform the benchmarking.

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WORK IN PROGRESS
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The `regreph` command is still work in progress

One of thie things not working right now is the benchmarking of the refspec.
It does not find the tests.
Make Bench classes immutable

Bench and BenchFile are now immutable.
You cannot change their results/file after they've been constructed.

You can no longer set the whole results array on a BenchResults instance.
You could just add test results to the instance.

The setters were not really needed and this ensures the results stay
the same.