Merge changes from topic "am-b48636b17b6249d997779ca51ed7a029" into udc-mainline-prod

* changes:
  Fixes @Nullable issues in System UI and WMShell.
  Fix kotlin nullable errors in frameworks/base
  Fix kotlin nullable errors in PermissionService.
  Fix kotlin nullable errors in SilkFX tests
  Fix kotlin nullable errors in PackageInstallerSessions
  Fix kotlin nullable errors in Input tests
  Fix kotlin nullable errors in EasterEgg
  Fix kotlin nullable errors in perftests
  Fix kotlin nullable errors in SettingsLib
  Fix kotlin nullable errors in CredentialManager
  Fix kotlin nullable errors in services.permission