Switch BandwidthController per-UID commands to iptables-restore

Bug: 32073253
Test: bullhead builds and boots
Test: netd_{unit,integration}_test pass
Test: Turning datasaver on/off changes rules as expected
Test: Modifying datasaver whitelist changes rules as expected when datasaver is on
Test: Adding and removing cell data limits changes rules as expected
Test: No IptablesRestoreController methods in normal usage
Change-Id: I83723db6a539b641308ef0f74ac30b4db304295c