Add privacy dot flag for SystemUI

Add privacy dot flag, it is used to clearly indicate related components
to keep the maring spaces, or add related overlay views for it.

And also prevent NPE issues at b/199060326 even the phone configs for
cutout or rounded conrner are incorrect.

Detail:
1. ScreenDecorations:
   a.Read privacy dot flag, and follow original
   shouldShowRoundedCorner() method logic to provide another
   shouldShowPrivacyDot() method. The existence of privacy dot container
   is determinated throguht the return value of shouldShowPrivacyDot().
   b. DisplayCutout::getCutout is a sync method, cache the return value
   as local variable.
2. KeyguardStatusBarView: update keyguard status bar left/right margin
as this config.
3. StatusBarContentInsetsProvider: update phone status bar left/right
margin as this config

Bug: 190922585
Bug: 199060326
Bug: 199463850
Test: atest com.android.systemui.ScreenDecorationsTest
Change-Id: If1aa97b877ba374d6fa47615591bb91a4ebab421