Move the tests from .html to .sky

sky/tests/custom-elements/resources/document-register-fuzz.sky

 <script>
 function setupObjectHooks(hooks)
 {
     // Wrapper for these object should be materialized before setting hooks.
     console.log;
     document.register;
 
     Object.defineProperty(Object.prototype, "prototype", {
         get: function() { return hooks.prototypeGet(); },
         set: function(value) { return hooks.prototypeSet(value); }
@@ skipping 40 matching lines @@
          }
     } catch (e) { console.log(e); }
 }
 
 this.exports = {
     setupObjectHooks: setupObjectHooks,
     exerciseDocumentRegister: exerciseDocumentRegister,
     register: register,
 }
 </script>