`activeItems` not preserved even if keepScrollPosition = true

Testing #133891 1. Have the following extension. 2. Run the extension. F1 > hello world 3. Notice how the scroll position is not preserved when the new items get added to the quick pick 🐛 ```Tyepscript import * as vscode from 'vscode'; export function activate(context: vscode.ExtensionContext) { let disposable = vscode.commands.registerCommand('sep-ext.helloWorld', async () => { const pick = await vscode.window.createQuickPick(); pick.keepScrollPosition = true; const items = [{ label: 'january' }, { label: 'february' }, { label: 'march' }, { label: 'april' }, { label: 'may' }, { label: 'june' }, { label: 'july' }, { label: 'august' }, { label: 'september' }, { label: 'october' }, { label: 'november' }, { label: 'december' }];; pick.items = items; pick.show(); let i = 0; setInterval(() => { items.push({ label: String(i++) }) pick.items = items; }, 500); }); context.subscriptions.push(disposable); } export function deactivate() { } ```