virtual-scroll: support using elements that have parent requirements as virtual scroll items

[mmalerba]

Add support for using tags such as <li>, <tr>, and <td> that have constraints on legal parent tags as items in a virtually scrolling list.

[amcdnl]

If you make the component a attribute selector, this will work fine. I'm doing this with SVG elements.

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}