Make RippleDrawable as the only background drawable to be borderless

If we use LayerDrawable with RippleDrawable as one of its layer, due to
the RippleDrawable is a borderless drawable, the entire LayerDrawable
would try to render outside of the views bound where you'd see a circle
over the footer buttons.

By moving the adaptiveIcon as the ImageView's source and use
RippleDrawable as the only background drawable, we're able to keep the
RippleDrawable as borderless, and won't see the AdaptiveIconDrawable
being rendered over the footer view.

Bug: 361454352
Test: manual. Maxout the display and font size and view the a11yMenu on
phone in landscape mode, verify no overlapping images on footer view.
Also verify the Ripple affect is still borderless.
Flag: EXEMPT low risk bugfix

Change-Id: I8c30dab3c52b3c821fdb067d93b755a4ed040587