DO NOT USE THIS INSTANCE FOR LIVE DATA!!!!
YARN-8016 and YARN-8948 add functionality to initialize placement rules with ResourceScheduler. We need this in branch-2, but it doesn't apply cleanly. Hence we just port the initialization logic.
YARN-8948 PlacementRule interface should be for all YarnSchedulers
YARN-8016 Refine PlacementRule interface and add a app-name queue mapping rule as an example