trees: always handle an twistie events by the tree if it changes collapsed state (microsoft#209090)

This allows preserving your multi-selection while expanding/collapsing other nodes in the tree. I think this is a good overall change to make across our UI. E.g. similarly, without this change, you can't expand a folder in the Explorer view without losing your selection state. cc @joaomoreno

Fixes microsoft#208852

Author: connor4312

src/vs/base/browser/ui/tree/abstractTree.ts

@@ -2295,7 +2295,7 @@ class TreeNodeListMouseController<T, TFilterData, TRef> extends MouseController<
 			this.tree.setFocus([location]);
 			this.tree.toggleCollapsed(location, recursive);
 
-			if (expandOnlyOnTwistieClick && onTwistie) {
+			if (onTwistie) {
 				// Do not set this before calling a handler on the super class, because it will reject it as handled
 				e.browserEvent.isHandledByList = true;
 				return;