When cloning the InternalList, pass through properties that aren't rebuilt

InternalList.clone() assumed that all properties are automatically rebuilt
when a new document is built, but that's not true for .nextUniqueNumber
(or for .itemHtmlQueue for that matter). This meant that, in practice,
.nextUniqueNumber was being reset to 0 after auto/N numbers for existing
references had been assigned, but before assigning numbers to newly
created references. This caused all sorts of naming collision fun.

Bug: 54712
Change-Id: I1d087a5f3c23979d7d488e3ab32eb064ebc23e94
Merge "When cloning the InternalList, pass through properties that aren't rebuilt"