This allows us to move Parsoid-specific extension code from the
Parsoid repo into the extension's own repository and still have
Parsoid parser tests run on it via core's mechanism for running
extension tests.
Factored out some common ParserOptions setup into a common helper
function. There are a number of features still missing from the
Parsoid test runner, which are marked with @todo comments and
phab task numbers.
Bug: T254181
Change-Id: Ifaf53862b96e9127d8f375ad8dd0cc362cba9f5b
