gd/hci: support handle_msft_events in msft

This patch supports the Microsoft advertisement monitor event, i.e.
MSFT_LE_MONITOR_DEVICE_EVENT.

Note that the first octet of the vendor prefix, which is unique in
a vendor controller, is registered via the vendor specific event
manager so that the the vendor specific event manager can dispatch
the Microsoft event properly.

Bug: 246404026
Tag: #floss
Test: ./build.py --target test
Test: mm
Test: Manual test on a ChromeOS devic
BYPASS_LONG_LINES_REASON: Bluetooth likes 120 lines

Change-Id: I79482297c640d4b89e9a7579d5a3b2190a175822