Compile-fun takes advantage of sorted output of "renumber", avoids CFA

Compile-fun takes advantage of sorted output of "renumber", avoids CFA

* module/language/cps/dfg.scm ($dfg): Rename nvars and nlabels fields to
  var-count and label-count.  Export dfg-min-var, dfg-min-label,
  dfg-label-count, dfg-var-count.

* module/language/cps/compile-bytecode.scm (compile-fun): No need to
  build a CFA given the renumbering pass.  Adapt to treat labels as
  ordered small integer in a contiguous vector.