Add adb_root daemon and hooks

Author: Luca Stefani <luca.stefani.ge1@gmail.com>
Date:   Sat Nov 2 22:46:12 2019 +0100

    Add adb_root daemon

    Change-Id: I516f1b85e28f5d061c8c54282a7657d53162bccb

Author: Luca Stefani <luca.stefani.ge1@gmail.com>
Date:   Sat Nov 2 23:54:43 2019 +0100

    Add adb root hooks

    Change-Id: I6b42ae84ab22ed4e86b92c3c1276a44a14d61781

Author: dianlujitao <dianlujitao@lineageos.org>
Date:   Sun Nov 17 23:21:36 2019 +0800

    Create /data/adbroot on post-fs-data

     * The real /data partition is not available before this stage.

    Change-Id: I2cbcd788f35a2d51c823a71e2c944502812c1cfd

Author: dianlujitao <dianlujitao@lineageos.org>
Date:   Sat Nov 23 20:55:42 2019 +0800

    adbd: Initialize adbroot status to false

    Change-Id: I6d5dc84974dff1a219702fb628e08517848977eb

Author: dianlujitao <dianlujitao@lineageos.org>
Date:   Sat Nov 23 20:58:31 2019 +0800

    adbd: Make adbroot interface a static lib

    Change-Id: I40e46b8312ec77992fc1c11d2190b611bfd049cb

Author: dianlujitao <dianlujitao@lineageos.org>
Date:   Sun Nov 24 16:24:27 2019 +0800

    adb_root: Enforce caller UID

     * AID_SYSTEM - Settings app
     * AID_SHELL - adbd
     * Apply minor clean up while at it

    Change-Id: I15a5d18204a96cc2f8352a6cc7f6f901193aa5b9

Author: dianlujitao <dianlujitao@lineageos.org>
Date:   Sun Nov 24 16:39:11 2019 +0800

    adb_root: Add mutex to binder interface

     * Binder IPC is not implemented in a thread-safe manner, add mutex to
       avoid possible race.

    Change-Id: I37cdca33d519b0fc960960272790d1f55874e2e2

Author: dianlujitao <dianlujitao@lineageos.org>
Date:   Sun Nov 24 17:01:49 2019 +0800

    adb_root: Restart adbd when turning off root

     * The running adbd session remains rooted after turning off from UI.

    Change-Id: Iedd5282b4e3c11ef6c0959ae6867448521cb2c78

Author: PIPIPIG233666 <pig.priv@gmail.com>
Date:   Sat Dec 21 11:23:43 2019 -0500

    adb_root: Run adb_root with system group

    * Avoid the need to rely on dac_override

    Change-Id: I4ba218f7c613c34aa6739f186102460b6f11b873

Change-Id: Ib4089593c2c3e384087f1abf1951e3c066764362