* Rather than computing TOC HTML in Parser and setting it in
ParserOutput, compute it on demand based on section metadata.
This will let Parsoid set section metadata in ParserOutput
and have the TOC generated automatically.
* This required fixing some "bugs" in Linker's generateTOC
which didn't properly close tags and relied on Tidy to fix
up unclosed li and ul tags.
* This patch relies on converting section metadata objects to
array objects, but Linker::generateTOC could be converted to
use TOC data instead.
* Since TOC generation is now moved to getText(), this is done
post-PC load and this eliminates the parser cache split on
user language for TOC heading localization.
Bug: T293513
Change-Id: Ief1bba326d3612b40930440c872a61abadffab10
439656e019