Fix inputbox onTriggerButton() event

[tortmayr]

What it does

Ensure that the clicked button is correctly forwarded to event handlers when using InputBox.onDidTriggerButton (Plugin API).

The interface definition of QuickInputButtonHandle expects an index property but monaco actually calls the property handle

Fixes #13077

Contributed on behalf of ST Microelectronics

How to test

Create a simple plugin that opens a QuickInputBox with two buttons and log the onDidTriggerButton event.
On master the event is always undefined. With this change the clicked button is correctly forwarded to the event handlers.
e.g:

export async function activate(context: vscode.ExtensionContext) {

		const inputBox = vscode.window.createInputBox();
		const addButton={
			iconPath: new vscode.ThemeIcon('add'),
			tooltip: 'Add Item'
		};
		inputBox.buttons = [vscode.QuickInputButtons.Back, addButton ];
		await new Promise<void>(resolve => {
			inputBox.onDidTriggerButton(event => {
				console.log(event);
			});

			inputBox.onDidAccept(() => {
				resolve();
			});

			inputBox.show();

		});
}

You can also use this example plugin:
quickpick-0.0.1.zip

Follow-ups

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• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

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[jfaltermeier]

Thanks, lgtm!
I've tested with the attached plugin in electron and browser.

[JonasHelming]

@tortmayr I guess you can merge this!