Don't use quotations to load a model. Though use of node.getModel is much more straightforward (and doesn't require hacks in StaticReference impl to resolve ref targets), it's not perfect as repository we resolve node in is implicit. This might not be the greatest concern here, as we expect closures RT to be always available, however in general node/xxx/ approach might need attention.
Use RuntimeFlags instead of hardcoded stings throughout code.
GenerationSession: drop deprecated code
Revert the change unless RuntimeFlags got better place to live at (somwhere startup and mps-boot.jar can find it).
Beautify.
NPE from JavaClassStubModelDescriptor when MPSModuleRepository is being disposed: track model loaded state and ask for internal model only when there's a justified confidence it won't trigger model load when we don't really need one.
Favor code reuse to brevity