Decouple bt_facade_helpers with bt_packets

What we really need is converting a packet into Bytes or Vec<u8>.
Implement From<SomePacket> for them. Then in facade/helpers, we can get
rid of packet dependency.

Test: compile on android and chromeos
Bug: 191711152
Tag: #gd-refactor
Change-Id: I34178167ff7f012c3dc596a96fefc57b258195fe