SystemUI: Add tunables for clock position

Author: LuK1337 <priv.luk@gmail.com>
Date:   Wed Aug 1 18:10:39 2018 +0200

    SystemUI: Initialize mClockVisibleByUser to android:visibility

    * Fixes ~ triple clock ~ after leaving from Google SUW.

    Change-Id: I3ceea4400b3057e2b6b1f221f9074b1d451133ea

Author: Luca Stefani <luca.stefani.ge1@gmail.com>
Date:   Sun Jul 29 14:19:08 2018 +0200

    SystemUI: Fix default clock blacklist value

    Change-Id: Ibdc4f6a707569ddb417854760cf579daca989ebb

Author: LuK1337 <priv.luk@gmail.com>
Date:   Tue Apr 2 20:56:25 2019 +0200

    SystemUI: Don't hide right clock when heads up is visible

    * https://gitlab.com/LineageOS/issues/android/issues/436

    Change-Id: I85a6cd2dff79e6b97d8a7db552c22d611bf25dbd

Author: LuK1337 <priv.luk@gmail.com>
Date:   Thu Sep 27 12:24:19 2018 +0200

    SystemUI: Fix clock icon blacklist handling

    * This makes sure clock isn't on blacklist before
      calling showClock(animate);

    Change-Id: I7f77a83aa6c109e1682d764fb22701375ae5ba1e

Author: Hendrik Hagendorn <git@finnq.de>
Date:   Sun Jan 15 10:00:12 2017 +0100

    Tuner: Move clock seconds option to status bar settings

    Change-Id: I532c179f06b934009d48433e50b69660247ee295

Change-Id: Icdc039d13fd2676c1eb979a81fb77f9a6ec59b4a