Non-system users can now have restricted profiles

In the non split system user, only USER_OWNER is allowed to have restricted
profiles. This is now changed in split user mode, where multiple secondary
users can have restricted profiles.

Added UserInfo.restrictedProfileGroupId field, which defines parent/child
relationship between secondary users and linked restricted profiles. Adjusted
shared accounts handling logic to not assume that USER_OWNER is the only owner.

Bug: 23191995
Change-Id: I5f3fc2aa4f229103d6e75ec2c3dfce866b8007de