ProjectPane: refactor to keep structure and ui update of project tree for primary project pane only (not for project element selectors that use ProjectTree, not ProjectPaneTree); use MPS project where reasonable; fix UI update thread to wait for more updates to come at the first start, make it start as expected (timer.resume() doesn't respect initial delay), process ui changes at once (in batches, though), not in 500ms ticks
MPS-20274: error invocation method: "nodeSubstituteActionsBuilder_ActionsFactory_ClassifierMember_3609453419506189063" in jetbrains.mps.baseLanguage.actions.QueriesGenerated. Null model due to stale cache in FNF - track model load/unload events (and few other lifecycle events, as well), and drop FNF, if any.