RootCanal: Remove h4_packetizer_lib to device/google/cuttlefish

The library is only used by the bt_vhci_forwarder tool.
Remove the sources that are only used by the library,
and the HciProtocol abstraction that unified H4Packetizer
and H4DataChannelPacketizer.

Bug: 256013143
Test: atest rootcanal_test_host
Change-Id: I60cde0d36c1643251fd6464f3afa90af90d871b6