Desks: Always set |userIdToProfileIdsMap| on init

Partially reverts If05494258ac9426e685f654fdc44f740587bf06a. Setting the
user to profile map on init is still needed in case the current
repository is accessed between init and onInit().

Flag: com.android.window.flags.enable_multiple_desktops_backend
Bug: 411276711
Test: atest DesktopUserRepositories
Change-Id: I5dda0500b2eb62e3fa67df659ff8417e3a18c05f