When the `enclose` attribute is used `syntaxhighlight-enclose-category`
is added, and when a <source> tag is used, the
`syntaxhighlight-source-category` is used.
Parser tests verify the tracking category is added when appropriate.
Bug: T241636
Bug: T237267
Change-Id: I7a21c635de426ab024703c04acdc6fa2184daedb
Do this by having SyntaxHighlight_GeSHi::highlight() return a Status object
rather than a plain string, and by making it the highlight method's job to look
up a lexer for a language. The actual warning text is not outputted anywhere
yet; deferring that for a follow-up patch.
Bug: T103586
Change-Id: Id839f925a56ab09a8423958327b9aefd7207ef37
