Brings back "Control from locked device" setting.

In ag/20427460, we made ControlsTrivialPrivacyPreferenceController, which controls this setting, be UNSUPPORTED_ON_DEVICE if customizable lock screen quick affordances are enabled.

This wrongly removes this setting from the Settings app and there is no new UI where the user can control that anymore. What this means is that, once users upgrade to an Android build with our feature, they will forever be stuck with whatever they last chose for "Control from locked device".

This CL brings that back but changes the behaviour a bit such that, if
the quick affordances feature is enabled, this setting is never
disabled.

Fix: 260722836
Test: Unit tests added. Manually verified that the setting is visible
and enabled if the feature is enabled, even if the current selection
does not include the Home quick affordance and that if the feature is
off, the setting is visible but disabled if the main setting is off (old
behaviour unchanged).

Change-Id: I2e53123b3b7a2896699aeaa13b0c7d5a1c8a9c92