The TokenTransformDispatcher now actually implements an asynchronous, phased
token transformation framework as described in
https://www.mediawiki.org/wiki/Future/Parser_development/Token_stream_transformations.
Additionally, the parser pipeline is now mostly held together using events.
The tokenizer still emits a lame single events with all tokens, as block-level
emission failed with scoping issues specific to the PEGJS parser generator.
All stages clean up when receiving the end tokens, so that the full pipeline
can be used for repeated parsing.
The QuoteTransformer is not yet 100% fixed to work with the new interface, and
the Cite extension is disabled for now pending adaptation. Bold-italic related
tests are failing currently.
