Add support for getting the detail of a QuickPickItem #2030

Describe the request

A QuickPickItem in VS Code is composed of three main elements:

• label
• description
• detail

Currently, vscode-extension-tester provides an API to retrieve only the description and the label (see Input.ts).

I would also like to be able to get the detail of the QuickPickItem.

Usage

I develop an extension where my QuickPickItems are composed of labels and details, representing paths.

If the path from label exceeds a number of segments, I will trim it to the left.

The detail will contain the full path, and I would like to verify if this full path is correct.