Make disabled by policy tiles look UNAVAILABLE

Tiles that are disabledByPolicy will have the same looks as a
STATE_UNAVAILABLE tile. The accessibility action on click will read
"Double-tap to learn more", and the state description will add the
corresponding "Unavailable" text

Test: manual using TestDPC and TalkBack.
Test: atest QSTileViewImplTest QSIconViewImplTest
Fixes: 237643526
Change-Id: I40d65b58c14fe30a6fdb3c07da3c9c94579e7712