Atom: Add BluetoothLinkLayerConnectionEvent atom

* Add this atom to report events related to Bluetooth link layer
  connection, including:
  - Obfuscated ID of remote device
  - Connection handle
  - Direction of the connection
  - Type of the connection
  - Associated HCI command and/or event
  - Status code associated with HCI command and/or event
  - Reason code associated with HCI command and/or event
* Add enum definitions for HCI commands and events as defined in the
  Bluetooth 5.0 specification
* Add enum definitions for link type and direction

Bug: 112969790
Test: make, test drive with statsd
Change-Id: I0fdc59274d49ad503e9ba9cf8f49c9d8872a4131