After T, Bluetooth tethering could use a random address. But if we keep
putting the legacy Bluetooth address in the cache, the coordinator will
always assign the legacy address first until it runs into a conflict.
This change in itself does not do anything. Once we have a
trunk-stable namespace for mainline beta, we will add a flag for
this change, and check the flag in PrivateAddressCoordinator.
Bug: 287177081
Test: new unit tests
Flag: EXEMPT no behaviour changes
Change-Id: I56810b5b0e1098a5f89cbb1ad665d2b8652e860c
acd7366b65