Hide conversation bubble switch if app bubbles are off

Fixes: 159340745

Test: BubblePreferenceControllerTest

Test: priority conversation bubble
=> app bubbles OFF => toggle hidden
=> selected bubbles ON => toggle checked
=> app bubbles ON => toggle checked

Test: default/silent conversation bubble
=> app bubbles OFF => toggle hidden
=> selected bubbles ON => toggle NOT checked
=> app bubbles ON => toggle NOT checked

Change-Id: Ia5759c2a06c1da4d84b3dafed95e52c3aa30ad56