Use annotations for taint in Parser & ParserOutput.

Use annotations for taint in Parser & ParserOutput.

This replaces the builtin taints that are removed in
Ic1e1983a51c. Additionally, parse will no longer warn about
double escaping - there's many situations where such warnings
are wrong (e.g. Using Html::rawElement()). However this also
means that Parser::parse( wfMessage( 'foo' )->parse() ); will
no longer give a double escaping warning, which is unfortunate.

Bug: T202380
Change-Id: Ia52d37411beb62b112c6ff102438063c3d750769