Merge changes Idf9e6f2f,Ibd145e12,Ibc258ebb,Ie1b3c077,I9897edd3, ...

* changes:
  Add bluetooth_gd_hci_fuzz_test
  Add FuzzingHciHal, to inject fuzzed input up the stack
  Add DevNullHci, to facilitate fuzzing the hci layer
  Add SentinelWorkItem, to allow posting a work item and waiting for completion
  Add gd/fuzzing/helpers
  Add DevNullQueue, a fuzzing helper to drop stuff