Steps to reproduce (assumes ChromeVox or similar))

1. Open https://elastic.github.io/eui/#/layout/popover in a new tab.
2. Tab to the first "Show popover" button
3. Press enter
4. Note the popover appears but is not read
5. Tab to the next "Show popover" button under the "Trap focus" section
6. Press enter

This reacts more like I would expect, however I see the need to have the ability to explicitly set ownFocus. The popovers still need to be read, though... I'm wondering if there's some sort of aria-describedby trick we can use here.

Category: #728: Elastic UI Popover Accessibility
Relevant WCAG Criteria: 3.3.2 Input Assistance: Labels or Instructions