Support bluetooth not using MultinetworkPolicyTracker

This required advancing the IpManager to IpClient refactoring
(Bluetooth used IpManager and friends). Most importantly, the
Bluetooth code used WaitForProvisioningCallback, so this is
moved into IpClient proper now. Also: some more renaming
cleanup.

Test: as follows
    - built
    - flashed
    - booted
    - runtest frameworks-net passes
Bug: 62476366
Bug: 72663849

Change-Id: I9eee2a9d5c31cdd48a054a7edc3403584efb1864