Use contains() algorithm from libsupport.
Rearrange transmit and receive methods together.
Stop stream channel on destruct.
Add dummy acknowledge() method.
Add stubs for two more required functions.

tx_reset() and rx_substream() are used in the attach packet handler.
We'd need to fix the back pointers to streams eventually.

Need to keep track whenever these streams are added-removed.
rx_detach_packet() handler unimplemented.
Fill in missing part of set_usid().
Log more info about attach packet.
Fill in rx_attach_packet() implementation.