attributes in AccessiblePeer should all use setAttributeToElement

[jessegreenberg]

From #893 @zepumph pointed out that it would be better if all attributes used the function that was made for this for consistency.

[jessegreenberg]

Took a look at this and I am now questioning the decision. There are three places outside of setATtributeToElement that set an attribute. Two were straight forward, but the third is in AccessiblePeer.setVisible

        for ( var i = 0; i < this.topLevelElements.length; i++ ) {
          var element = this.topLevelElements[ i ];
          if ( visible ) {
            element.removeAttribute( 'hidden' );
          }
          else {
            element.setAttribute( 'hidden', '' );
          }
        }

It is nice to be able to apply hidden to attributes in a loop without having to go through the "name" of the element like AccessiblePeer.CONTAINER_PARENT.

[jessegreenberg]

On the other hand, this is exactly where we would want to use the asProperty option so we don't have to do element.setAttribute( 'hidden', '' );

[jessegreenberg]

Done in the above commits. For setVisible I added an element option to setAttributeToElement to set the attribute directly to the desired element rather than looking up by name.

I considered replacing this entirely with the elementName option, but that would have required using getElementByName at every usage of setElementToAttribute so I decided against it.

Local tests are passing, closing this issue.