Strip ANSI colour escapes from STDOUT and STDERR when streams are not TTY

[aslakhellesoy]

When cucumber-js' STDERR or STDOUT is redirected to a file, there are still ANSI escapes in the output.

We should remove ANSI escapes when writing to a non-TTY stream.

One of the reasons we should do this is that the suggestion to redirect STDERR to a file in #1458 makes it difficult to read the contents written to that file:

�[32m�[1m┌──────────────────────────────────────────────────────────────────────────┐�[0m
�[32m�[1m│�[0m View your Cucumber Report at:                                            �[32m�[1m│�[0m
�[32m�[1m│�[0m �[1m�[36m�[4mhttps://reports.cucumber.io/reports/59fbb8b0-a625-4f0e-8c5b-284b95387f03�[0m �[32m�[1m│�[0m
�[32m�[1m│�[0m                                                                          �[32m�[1m│�[0m
�[32m�[1m│�[0m �[1mThis report will self-destruct in 24h.�[0m                                   �[32m�[1m│�[0m
�[32m�[1m│�[0m Keep reports forever: �[4m�[1m�[36mhttps://reports.cucumber.io/profile�[0m                �[32m�[1m│�[0m
�[32m�[1m└──────────────────────────────────────────────────────────────────────────┘�[0m

Since the ANSI escapes in this case come from the Cucumber Reports server (and not our own code), I suggest we implement this like this:

const stderr = process.stderr.pipe(replaceAnsiStream())
const stdout = process.stderr.pipe(replaceAnsiStream())

See https://github.com/chalk/strip-ansi-stream

Also see #1050 which didn't really solve the problem of stripping ANSI - it just disallows using formatters that output ANSI.