Add the Private Space app to preinstalled apps on AOSP.

The change is not flag guarded but all the components in the app are fag guarded under the android.multiuser.enable_moving_content_into_private_space flag. It will be installed only on private profiles[1] and will contain logic to move/copy files from other profiles to the private space.

[1]: https://source.corp.google.com/h/googleplex-android/platform/superproject/main/+/main:frameworks/base/data/etc/preinstalled-packages-platform.xml;l=143-146;drc=6f2466a236080a8a92723c148888d8d96ddb5a6f

Test: Infra only
Flag: EXEMPT config only
Bug: 394020467
Change-Id: Ib8f84cee2332398e66a3e4d09afc9c077c983829