Drawer with modalType="alert" should be dismissible with Escape

[ling1726]

For reference: #28276 (comment)

To be compliant with the WAI-Aria best practices, alertdialogs should be dismissible with Escape. Open/close state can be controlled in userland to create undismissible dialogs if required. We should be using the most accessible patterns by default

[marcosmoura]

By default, the Drawer follows the same behavior as Dialog, so that is also reflected.
The example we have in Drawer docs uses the controlled state to prevent closing. I made an update to the storybook description to explain that a little better.