cephadm: move colored output support into logging.py

cephadm: move colored output support into logging.py

Rewrite cephadm's colored output support such that it abstracts away
the colorization into extra logging metadata. The new code will not
unconditionally put control characters into the log files. It will
only print the control chars if the stderr is a tty.
In theory this is probably more future proof as well, but it's only
got two callers so it is hard to say how useful it'll be.

Signed-off-by: John Mulligan <jmulligan@redhat.com>