Subsystem parsers should be created lazily when needed

Currently when we register parsers for different versions of subsystem schema we always pass over instance of whole parser which is usually statically initialized.
In practice legacy (non current) parsers are only used rarely and there is no point in having them loaded in memory when not needed.

Impl should be based on provider pattern and as such also allow us to on demand create new instance of parser when needed, as well as enable us for parsers to be GCed, when they are not in use.