This is a precursor to be being able to build an intrusive list of PacketBuffers for use in queuing disciplines being implemented. Updates #2214 PiperOrigin-RevId: 302677662
Fixes #1510 Test: - stack_test.TestForwardingWithStaticResolver - stack_test.TestForwardingWithFakeResolver - stack_test.TestForwardingWithNoResolver - stack_test.TestForwardingWithFakeResolverPartialTimeout - stack_test.TestForwardingWithFakeResolverTwoPackets - stack_test.TestForwardingWithFakeResolverManyPackets - stack_test.TestForwardingWithFakeResolverManyResolutions PiperOrigin-RevId: 300182570