Fix for accessibility focus in custom snackbar

the FAB produces a custom snackbar on dismissal, upon which an erroneous UI element can become focused in talkback and produce confusing text output.
By correctly flagging the non-interactive parts of the FAB's hierarchy, we should be able to prevent this from occurring.

Test: Dismiss the FAB while talkback is active. Focus should not shift to an unexpected element.
Flag: aconfig FLOATING_MENU_DRAG_TO_HIDE DISABLED
Bug: 322855605

Change-Id: I05ea3e16adc97a0ce88adcdc0149bb9c2bfe3463