Close the form attachment popup upon Escape key press

**Background.** On the form attachments page (the `FormAttachmentList` component), if the user drops one or more files onto the page (or uses the "Upload files" button to select one or more files), then a popup (`FormAttachmentPopups`) appears. The popup contains one or more buttons, one of which is automatically focused.

When the popup (or an element within it) is focused, then if the user presses the Escape key, the popup should close. Right now it does not.

Start by locating the FormAttachmentList and FormAttachmentPopups components and reproduce the behavior after dropping files or using the "Upload files" button. Check the focused popup or child element's Escape-key handling. Done means pressing Escape while the popup or one of its elements is focused closes the popup.

Written by the indexing model from the issue text.