Use getProfileParent instead of isSameProfileGroup.

There are use cases that the caller only has INTERACT_ACROSS_USERS
which is not enough to call isSameProfileGroup. Instead use
getProfileParent which has the same required permissions as
getUserProperties that is already being used.

Bug: 439976184
Flag: com.android.documentsui.flags.support_visible_background_user
Test: atest DocumentsUIUnitTests

Change-Id: I1b2ce60259ae32d5c787d800824cabde33f1d1e3