escapable raw is not preserved when entering tornado_body state

[jimmyhchan]

this currently fails.

<textarea>
  {#foo}
     <span>should be raw text here </span>
  {/foo}
</textarea>

There is a similar issue in attrs but we have codes to fix all this.

Ideally, we should have a mechanism that knows how to connect a tornado body fragment to it's parent element placeholder based on the state it came from. Perhaps we can solve this generically for escapable_raw and attrs and namespaces and etc.