SystemUI: Resolve status bar battery percentage tints

 * Use the tint color matching the status bar texts

 * Results: Before and after: https://ibb.co/gvGm7y

 * Test: Bright wallpaper with status bar contrasts:
    https://ibb.co/dxupSy

Change-Id: Idff1060af9e0a0fc5eab3ed498b10266e3124950