Bringing back build colourisation - #7740

Changelog: Fix: Do not capture output for normal conan run (no logging or testing) when launching processes via ConanRunner so that color from build tools output is not lost.
Docs: omit

This is a proposal for recovering ConanRunner colorisation. Maybe we just want to capture the stdout using Popen and therefore disabling color codes when we are running the tests (the stream will be a StringIO) or when we explicitly set run_to_file=True or run_to_output=False.

Closes: #5597

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