GameSpace: Don't set device_config property directly

GTS don't allow any app to have the android.permission.WRITE_DEVICE_CONFIG permission
i.e we can't modify device_config property from our game space.

So write the property to our custom Settings.Secure.GAME_OVERLAY.
Then observe the value changes and set the property to the
device_config from GameManagerService.

Since GameManagerService is a part of system_server,
GTS will be happy.

Change-Id: I6e223f60608cebe974f5e4bdb863e4c0e0817fc4
Signed-off-by: minaripenguin <minaripenguin@users.noreply.github.com>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>