debugcommands: move 'debugrevlogopts' into the new module
This move contains the first reference to debugrevlogopts in
debugcommands.py. We'll eventually want to move that over. We
hold off for now because it would introduce a module import cycle.
#
# Avoid interference from actual test env:
unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL