Merge changes I099e53e6,Icab0e0d7,Ic8b73158,I989b35eb,Ie3bf7c90, ...

* changes:
  Assorted cleanup
  Simplify disconnect for cert channels
  Simplify sending information requests
  Add information response matchers
  Move dut & cert channels into return result
  Use multi-match in a few places where it makes sense
  Add function to send s_frames & clean up sending
  Rename L2capMatchers.InformationFrame & SupervisoryFrame
  Distingiush between validated and unvalidated channels open
  Simplify channel open, so it can fit on one line
  Migrate i frame sending into CertL2cap
  Start migrating to channel abstractions
  Make ertm & fcs separable, reduce redundant code
  Add function to simplify sending control packets