Merge changes I77101952,I399631c6,I5ea98a06,I0b243f45,I5554cd42, ... into main

* changes:
  Fix test comment
  Enable header compression when requested
  Implement 6lowpan header compression
  Add a basic CSTest for L2capNetworkProvider
  Release network reservations in tearDown
  Start L2capNetworkProvider in CS
  Revert "Join HandlerThread if BLE is not supported"