Candidates for AbstractRange

[annevk]

trafficstars

It seems the following members from Range might be suitable to move up to AbstractRange so StaticRange has them too:

  void collapse(optional boolean toStart = false);
  void selectNode(Node node);
  void selectNodeContents(Node node);

  [NewObject] Range cloneRange(); // with s/Range/AbstractRange/

The following seems reasonable as well, but would require a substantive change in signature as a StaticRange is not guaranteed to have a common ancestor container:

  readonly attribute Node commonAncestorContainer; // with s/Node/Node?/

cc @rniwa @johanneswilm @bzbarsky @dstorey @garykac