The previous "ALL" role was the OR of a bunch of other roles,
which is a mistake: it's better if "ALL" means "all".

The "NET_PARTICIPANT" role refers to the anything that is actively
building circuits, downloading directory information, and
participating in the Tor network.  For now, it is set to
!net_is_disabled(), but we're going to use it to implement a new
"extra dormant mode".

Closes ticket 28336.