strip source quote-aware and resolve dynamic class references

- strip # comments with quote-state tracking so a hash in a string no
  longer truncates the line
- skip heredoc bodies in every @(EOT) form so documentation text is not
  indexed as a class reference
- take every literal name out of a selector, following a bare variable
  through the assignments in its own file
- record a class reference that stays unresolved against its file, with
  any literal prefix, instead of dropping it
- read a class name case insensitively in a title or type reference
- tag each edge as a declaration or an ordering reference

internal/impact/testdata/repo/site/profiles/manifests/base.pp

@@ -5,5 +5,6 @@ class profiles::base {
   class { 'profiles::viaclass': }
   include profiles::cycle::a
   include profiles::listed::a, profiles::listed::b
+  include profiles::dynamic
   profiles::defined::thing { 'x': }
 }

internal/impact/testdata/repo/site/profiles/manifests/dynamic.pp

@@ -0,0 +1,3 @@
+class profiles::dynamic {
+  include "profiles::dyn_${facts['role']}"
+}