Add le_address_manager::UnregisterSync

During le_impl destruction there is no sync between
posting on event handler and deletion leaving handler
in undefined state

Bug: 227615854
Tag: #refactor
Test: gd/cert/run
BYPASS_LONG_LINES_REASON: Bluetooth likes 120 lines

Change-Id: I2321549421ca56258aff9c39b524787c80683e0c