Rename IpManager to IpClient

Test: as follows
    - built
    - flashed
    - booted
    - runtest frameworks-net passes
    - frameworks/opt/net/wifi/tests/wifitests/runtests.sh mostly passes,
      except for the following errors:

      java.lang.VerifyError: Rejecting class com.android.server.wifi.WifiNative_Proxy that attempts to sub-type erroneous class com.android.server.wifi.WifiNative (declaration of 'com.android.server.wifi.WifiNative_Proxy' appears in /data/data/com.android.server.wifi.test/app_dxmaker_cache/Generated_-1635506025.jar)

Bug: 62476366
Change-Id: I8b1ead03fe0b3eadcb803147c0d1890200feee36
6 files changed