Description

When trying to insert a block with the /block name syntax, the list box is no longer read to screen readers. This is because the aria-owns and aria-activedescendent attributes contain IDs out of the current iFrame scope causing a null error.

Step-by-step reproduction instructions

1. Open a post or page.
2. Go to insert a block by typing in the empty paragraph field. Something like /ima should do.
3. Arrow up and down.
4. Check to see the field now has the 2 ARIA attributes as mentioned in the description above.
5. Try to do a document.getElementByID() or document.querySelector() using the IDs from the ARIA attributes. The commands will return null.
   6.I believe this is because the Autocomplete component renders outside the iFrame. Needs a fix as this feature is completely broken for screen reader users.

Screenshots, screen recording, code snippet

No response

Environment info

WordPress: 6.2-alpha-54678
Browser: Firefox
Screen reader: NVDA
OS: Windows 10 Professional

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes