Allow constructing BluetoothDevice with anonymous address type

Define private value for anonymous address type defined in Bluetooth
Core 5.4 spec.

Value added to IntDef is private in BluetoothDevice class because it should
not be allowed to be used to create BluetoothDevice object by
application, and is passed directly from native in onScanResult
callback. Package private constructor not an option as is constructed from different package in the regression being addressed by this CL.

Test: m .
Test: manual: scan anonymous advertisement and ensure scan result is
delivered to application
Flag: EXEMPT fix for unflagged regression
Bug: 296988500

Change-Id: I8168c370ec63f48acd535ea4ef05c6d5e58c2a2d