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