Manipulation: Break reference copies in cloned properties

Fixes #15104

```
   raw     gz Compared to 1.x-master @ d4a998f62fde4b9347b99571a7d000b53731909a
   +95    +60 dist/jquery.js                                                   
   +22    +12 dist/jquery.min.js
```
`dest[ p ] !== support.cloneProps[ p ]` is not strictly necessary, but without it we'd be executing lines like `dest.removeAttribute("appendChild")`. I ultimately decided to avoid those by having the support property be element-valued, with all associated consequences.