Change the data structure of restrictions in UM

Background
* In an org-owned managed profile device, two admins
  can set user restrictions on a user. The current
  data structure of local user restrictions uses a
  SparseArray<Bundle> where the key is the userId
  and the value is the restriction bundle.
* The existing data structure cannot store both the
  target userId and the originating userId.

Changes
* Introduces RestrictionsSet data structure, which is now
  used as a replacement of SparseArray<Bundle>.
* Updates the data structure of local restrictions to
  SparseArray<RestrictionsSet>. The first key is the
  target userId and the second key is the originating userId.
* targetUserId -> originatingUserId -> restrictionBundle
* Numerous methods in UserManagerService and
  UserRestrictionsUtils had to be changed to support this.

There will be follow up changes to move the logic of
sorting the restrictions into local and global restrictions
to DPMS.

Bug: 149743941
Test: atest com.android.server.pm.UserManagerTest
      atest com.android.server.pm.RestrictionsSetTest
      atest com.android.server.pm.UserRestrictionsUtilsTest
      atest com.android.cts.devicepolicy.UserRestrictionsTest

Change-Id: I08c9d60aa7a5e7cc3c661aaa4ba6dcd4f218323b