Add cross-platform transfer transport flag support to LocalTransport

To enable the cross-platform transfer transport flag on the
LocalTransport, add `is_cross_platform_transfer_ios=true` to the secure
setting `backup_local_transport_parameters`.

Bug: 403956528
Test: manually tested on device
Flag: com.android.server.backup.enable_cross_platform_transfer
Change-Id: If8f651c9dd0b6553df138542d41b085c22860473