cxxrtl: order -On levels as localize, elide instead of the reverse.

cxxrtl: order -On levels as localize, elide instead of the reverse.

Historically, elision was implemented before localization, so levels
with elision are lower than corresponding levels with localization.
This is unfortunate for two reasons:
  1. Elision is a logical subset of localization, since it equals to
     not giving a name to a temporary.
  2. "Localize" currently actually means "unbuffer and localize",
     and it would be useful to split those steps (at least for
     public wires) for improved design visibility.