hubris#1804 resulted in needlessly opaque symptoms. This cleans up
"humility dump" to give a better error message when we have run out of
space, and adds a new option (--print-dump-breakdown) to explain where
the space went. This also cleans up the options a bit (e.g., ditching
the confusing -F; renaming --all to --extract-all, but perserving the
old name as an alias), makes the emulated code match what we actually
do in the RoT with respect to buffer sizing, and improves the message
when dumps are already present to guide the user to extract them
rather than overwrite them.
Draft comment: