Fix can't focus on learn more link.

Prior to this cl, we set learn more text not focusable,
it causes a11y services can't distinguish it as an action item.

Also do some clean up, because we only allow clean plain text for
title id, so we can simply make it as <TitleView>

Also, we make footer preference can't be selectable,
so it can group subcomponents to make more accessible.

Test: Verify on battery saver / a11y related page with talkback service
, switch access, voice access.
Fix: 216516546
FIx: 215478454
Fix: 215476405
Fix: 215484382
Fix: 215483374

Change-Id: I15e82f871107115650c347aa32db5fb29ee446f7