color: move 'debugcolor' into the 'debugcommands' modules
This is the last bits we needed to move out of the extensions. 'hgext/color.py'
now only contains logic to changes the default color behavior to 'auto'.
However, more cleanups are on the way and we need to document the new config
directly in core.
#
# Avoid interference from actual test env:
unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL