help: show advanced, experimental and deprecated extensions with --verbose
I noticed that phabricator and absorb weren't showing up, no matter what.
There's a related problem where commands for these extensions *do* show up
without --verbose. I'm not sure what the point of hiding the extensions, but
not the commands is.
local test passed
addgroupcopy test passed
clone test passed
lowlevelcopy test passed
slicing test passed
issnapshot test passed