FastNodeFinder: track structure aspect changes in a single place
FastNodeFinder: drop workaround for MPS-13831 as change listener doesn't track load state change event any longer (and can't get into deadlock. moreover, there's even no synchronized block with model access)
FastNodeFinder: drop node sorting (wasn't in use for a year now, and there's little reason to do it here - clients could sort, if needed).
Use openapi change listeners.
FastNodeFinder: drop SNodeOperations.getModelFastFinder() as it's (a) not a node operation, rather model; (b) there's no reason to expose FNF or FNFManager to BL world, where model.nodes (or its newly added counterpart, SModelOperations.getNodes()) would suffice.