Create an IQuickWidget (#190627)

To do this, I've pulled `QuickInputController` into its own file since `quickInput.ts` was getting too big...

And then I made another thing that extends `QuickInput` that hides pretty much everything but does allow for a title bar.

This could be useful for more "QuickWebView" type experiences if we wanna light anything like that up.

src/vs/editor/standalone/browser/quickInput/standaloneQuickInputService.ts

@@ -8,13 +8,13 @@ import { ICodeEditor, IOverlayWidget, IOverlayWidgetPosition, OverlayWidgetPosit
 import { EditorContributionInstantiation, registerEditorContribution } from 'vs/editor/browser/editorExtensions';
 import { IEditorContribution } from 'vs/editor/common/editorCommon';
 import { IThemeService } from 'vs/platform/theme/common/themeService';
-import { IQuickInputService, IQuickInputButton, IQuickPickItem, IQuickPick, IInputBox, IQuickNavigateConfiguration, IPickOptions, QuickPickInput, IInputOptions } from 'vs/platform/quickinput/common/quickInput';
+import { IQuickInputService, IQuickInputButton, IQuickPickItem, IQuickPick, IInputBox, IQuickNavigateConfiguration, IPickOptions, QuickPickInput, IInputOptions, IQuickWidget } from 'vs/platform/quickinput/common/quickInput';
 import { CancellationToken } from 'vs/base/common/cancellation';
 import { IInstantiationService } from 'vs/platform/instantiation/common/instantiation';
 import { IContextKeyService } from 'vs/platform/contextkey/common/contextkey';
 import { EditorScopedLayoutService } from 'vs/editor/standalone/browser/standaloneLayoutService';
 import { ICodeEditorService } from 'vs/editor/browser/services/codeEditorService';
-import { IQuickInputControllerHost, QuickInputController } from 'vs/platform/quickinput/browser/quickInput';
+import { QuickInputController, IQuickInputControllerHost } from 'vs/platform/quickinput/browser/quickInputController';
 import { QuickInputService } from 'vs/platform/quickinput/browser/quickInputService';
 import { once } from 'vs/base/common/functional';
 import { IQuickAccessController } from 'vs/platform/quickinput/common/quickAccess';
@@ -111,6 +111,10 @@ export class StandaloneQuickInputService implements IQuickInputService {
 		return this.activeService.createInputBox();
 	}
 
+	createQuickWidget(): IQuickWidget {
+		return this.activeService.createQuickWidget();
+	}
+
 	focus(): void {
 		return this.activeService.focus();
 	}